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Arithmetic derivative

From Rosetta Code
Arithmetic derivative is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

The arithmetic derivative of an integer (more specifically, the Lagarias arithmetic derivative) is a function defined for integers, based on prime factorization, by analogy with the product rule for the derivative of a function that is used in mathematical analysis. Accordingly, for natural numbers n, the arithmetic derivative D(n) is defined as follows:

  • D(0) = D(1) = 0.
  • D(p) = 1 for any prime p.
  • D(mn) = D(m)n + mD(n) for any m,n ∈ N. (Leibniz rule for derivatives).

Additionally, for negative integers the arithmetic derivative may be defined as -D(-n) (n < 0).

Examples

D(2) = 1 and D(3) = 1 (both are prime) so if mn = 2 * 3, D(6) = (1)(3) + (1)(2) = 5.

D(9) = D(3)(3) + D(3)(3) = 6

D(27) = D(3)*9 + D(9)*3 = 9 + 18 = 27

D(30) = D(5)(6) + D(6)(5) = 6 + 5 * 5 = 31.

Task

Find and show the arithmetic derivatives for -99 through 100.

Stretch task

Find (the arithmetic derivative of 10^m) then divided by 7, where m is from 1 to 20.

See also


C++[edit]

Library: Boost
#include <iomanip>
#include <iostream>
 
#include <boost/multiprecision/cpp_int.hpp>
 
template <typename IntegerType>
IntegerType arithmetic_derivative(IntegerType n) {
bool negative = n < 0;
if (negative)
n = -n;
if (n < 2)
return 0;
IntegerType sum = 0, count = 0, m = n;
while ((m & 1) == 0) {
m >>= 1;
count += n;
}
if (count > 0)
sum += count / 2;
for (IntegerType p = 3, sq = 9; sq <= m; p += 2) {
count = 0;
while (m % p == 0) {
m /= p;
count += n;
}
if (count > 0)
sum += count / p;
sq += (p + 1) << 2;
}
if (m > 1)
sum += n / m;
if (negative)
sum = -sum;
return sum;
}
 
int main() {
using boost::multiprecision::int128_t;
 
for (int n = -99, i = 0; n <= 100; ++n, ++i) {
std::cout << std::setw(4) << arithmetic_derivative(n)
<< ((i + 1) % 10 == 0 ? '\n' : ' ');
}
 
int128_t p = 10;
std::cout << '\n';
for (int i = 0; i < 20; ++i, p *= 10) {
std::cout << "D(10^" << std::setw(2) << i + 1
<< ") / 7 = " << arithmetic_derivative(p) / 7 << '\n';
}
}
Output:
 -75  -77   -1 -272  -24  -49  -34  -96  -20 -123
  -1 -140  -32  -45  -22 -124   -1  -43 -108 -176
  -1  -71  -18  -80  -55  -39   -1 -156   -1  -59
 -26  -72   -1  -61  -18 -192  -51  -33   -1  -92
  -1  -31  -22  -92  -16  -81   -1  -56  -20  -45
 -14 -112   -1  -25  -39  -48   -1  -41   -1  -68
 -16  -21   -1  -60  -12  -19  -14  -80   -1  -31
  -1  -32  -27  -15  -10  -44   -1  -13  -10  -24
  -1  -21   -1  -32   -8   -9   -1  -16   -1   -7
  -6  -12   -1   -5   -1   -4   -1   -1    0    0
   0    1    1    4    1    5    1   12    6    7
   1   16    1    9    8   32    1   21    1   24
  10   13    1   44   10   15   27   32    1   31
   1   80   14   19   12   60    1   21   16   68
   1   41    1   48   39   25    1  112   14   45
  20   56    1   81   16   92   22   31    1   92
   1   33   51  192   18   61    1   72   26   59
   1  156    1   39   55   80   18   71    1  176
 108   43    1  124   22   45   32  140    1  123
  20   96   34   49   24  272    1   77   75  140

D(10^ 1) / 7 = 1
D(10^ 2) / 7 = 20
D(10^ 3) / 7 = 300
D(10^ 4) / 7 = 4000
D(10^ 5) / 7 = 50000
D(10^ 6) / 7 = 600000
D(10^ 7) / 7 = 7000000
D(10^ 8) / 7 = 80000000
D(10^ 9) / 7 = 900000000
D(10^10) / 7 = 10000000000
D(10^11) / 7 = 110000000000
D(10^12) / 7 = 1200000000000
D(10^13) / 7 = 13000000000000
D(10^14) / 7 = 140000000000000
D(10^15) / 7 = 1500000000000000
D(10^16) / 7 = 16000000000000000
D(10^17) / 7 = 170000000000000000
D(10^18) / 7 = 1800000000000000000
D(10^19) / 7 = 19000000000000000000
D(10^20) / 7 = 200000000000000000000

Go[edit]

Library: Go-rcu

Using float64 (finessed a little) to avoid the unpleasantness of math/big for the stretch goal. Assumes that int type is 64 bit.

package main
 
import (
"fmt"
"rcu"
)
 
func D(n float64) float64 {
if n < 0 {
return -D(-n)
}
if n < 2 {
return 0
}
var f []int
if n < 1e19 {
f = rcu.PrimeFactors(int(n))
} else {
g := int(n / 100)
f = rcu.PrimeFactors(g)
f = append(f, []int{2, 2, 5, 5}...)
}
c := len(f)
if c == 1 {
return 1
}
if c == 2 {
return float64(f[0] + f[1])
}
d := n / float64(f[0])
return D(d)*float64(f[0]) + d
}
 
func main() {
ad := make([]int, 200)
for n := -99; n < 101; n++ {
ad[n+99] = int(D(float64(n)))
}
rcu.PrintTable(ad, 10, 4, false)
fmt.Println()
pow := 1.0
for m := 1; m < 21; m++ {
pow *= 10
fmt.Printf("D(10^%-2d) / 7 = %.0f\n", m, D(pow)/7)
}
}
Output:
 -75  -77   -1 -272  -24  -49  -34  -96  -20 -123 
  -1 -140  -32  -45  -22 -124   -1  -43 -108 -176 
  -1  -71  -18  -80  -55  -39   -1 -156   -1  -59 
 -26  -72   -1  -61  -18 -192  -51  -33   -1  -92 
  -1  -31  -22  -92  -16  -81   -1  -56  -20  -45 
 -14 -112   -1  -25  -39  -48   -1  -41   -1  -68 
 -16  -21   -1  -60  -12  -19  -14  -80   -1  -31 
  -1  -32  -27  -15  -10  -44   -1  -13  -10  -24 
  -1  -21   -1  -32   -8   -9   -1  -16   -1   -7 
  -6  -12   -1   -5   -1   -4   -1   -1    0    0 
   0    1    1    4    1    5    1   12    6    7 
   1   16    1    9    8   32    1   21    1   24 
  10   13    1   44   10   15   27   32    1   31 
   1   80   14   19   12   60    1   21   16   68 
   1   41    1   48   39   25    1  112   14   45 
  20   56    1   81   16   92   22   31    1   92 
   1   33   51  192   18   61    1   72   26   59 
   1  156    1   39   55   80   18   71    1  176 
 108   43    1  124   22   45   32  140    1  123 
  20   96   34   49   24  272    1   77   75  140 

D(10^1 ) / 7 = 1
D(10^2 ) / 7 = 20
D(10^3 ) / 7 = 300
D(10^4 ) / 7 = 4000
D(10^5 ) / 7 = 50000
D(10^6 ) / 7 = 600000
D(10^7 ) / 7 = 7000000
D(10^8 ) / 7 = 80000000
D(10^9 ) / 7 = 900000000
D(10^10) / 7 = 10000000000
D(10^11) / 7 = 110000000000
D(10^12) / 7 = 1200000000000
D(10^13) / 7 = 13000000000000
D(10^14) / 7 = 140000000000000
D(10^15) / 7 = 1500000000000000
D(10^16) / 7 = 16000000000000000
D(10^17) / 7 = 170000000000000000
D(10^18) / 7 = 1800000000000000000
D(10^19) / 7 = 19000000000000000000
D(10^20) / 7 = 200000000000000000000

Haskell[edit]

import Control.Monad (forM_)
import Data.List (intercalate)
import Data.List.Split (chunksOf)
import Math.NumberTheory.Primes (factorise, unPrime)
import Text.Printf (printf)
 
-- The arithmetic derivative of a number, which is assumed to be non-negative.
arithderiv_ :: Integer -> Integer
arithderiv_ 0 = 0
arithderiv_ n = foldr step 0 $ factorise n
where step (p, v) s = s + n `quot` unPrime p * fromIntegral v
 
-- The arithmetic derivative of any integer.
arithderiv :: Integer -> Integer
arithderiv n | n < 0 = negate $ arithderiv_ (negate n)
| otherwise = arithderiv_ n
 
printTable :: [Integer] -> IO ()
printTable = putStrLn
. intercalate "\n"
. map unwords
. chunksOf 10
. map (printf "%5d")
 
main :: IO ()
main = do
printTable [arithderiv n | n <- [-99..100]]
putStrLn ""
forM_ [1..20 :: Integer] $ \i ->
let q = 7
n = arithderiv (10^i) `quot` q
in printf "D(10^%-2d) / %d = %d\n" i q n
Output:
$ arithderiv
  -75   -77    -1  -272   -24   -49   -34   -96   -20  -123
   -1  -140   -32   -45   -22  -124    -1   -43  -108  -176
   -1   -71   -18   -80   -55   -39    -1  -156    -1   -59
  -26   -72    -1   -61   -18  -192   -51   -33    -1   -92
   -1   -31   -22   -92   -16   -81    -1   -56   -20   -45
  -14  -112    -1   -25   -39   -48    -1   -41    -1   -68
  -16   -21    -1   -60   -12   -19   -14   -80    -1   -31
   -1   -32   -27   -15   -10   -44    -1   -13   -10   -24
   -1   -21    -1   -32    -8    -9    -1   -16    -1    -7
   -6   -12    -1    -5    -1    -4    -1    -1     0     0
    0     1     1     4     1     5     1    12     6     7
    1    16     1     9     8    32     1    21     1    24
   10    13     1    44    10    15    27    32     1    31
    1    80    14    19    12    60     1    21    16    68
    1    41     1    48    39    25     1   112    14    45
   20    56     1    81    16    92    22    31     1    92
    1    33    51   192    18    61     1    72    26    59
    1   156     1    39    55    80    18    71     1   176
  108    43     1   124    22    45    32   140     1   123
   20    96    34    49    24   272     1    77    75   140

D(10^1 ) / 7 = 1
D(10^2 ) / 7 = 20
D(10^3 ) / 7 = 300
D(10^4 ) / 7 = 4000
D(10^5 ) / 7 = 50000
D(10^6 ) / 7 = 600000
D(10^7 ) / 7 = 7000000
D(10^8 ) / 7 = 80000000
D(10^9 ) / 7 = 900000000
D(10^10) / 7 = 10000000000
D(10^11) / 7 = 110000000000
D(10^12) / 7 = 1200000000000
D(10^13) / 7 = 13000000000000
D(10^14) / 7 = 140000000000000
D(10^15) / 7 = 1500000000000000
D(10^16) / 7 = 16000000000000000
D(10^17) / 7 = 170000000000000000
D(10^18) / 7 = 1800000000000000000
D(10^19) / 7 = 19000000000000000000
D(10^20) / 7 = 200000000000000000000

J[edit]

Implementation:

D=: {{ +/y%q:1>.|y }}"0

In other words: find the sum of the argument divided by each of the sequence of prime factors of its absolute value (with a special case for zero -- we use the maximum of either 1 or that absolute value when finding the sequence of prime factors).

Task example:

   D _99+i.20 10
_75 _77 _1 _272 _24 _49 _34 _96 _20 _123
_1 _140 _32 _45 _22 _124 _1 _43 _108 _176
_1 _71 _18 _80 _55 _39 _1 _156 _1 _59
_26 _72 _1 _61 _18 _192 _51 _33 _1 _92
_1 _31 _22 _92 _16 _81 _1 _56 _20 _45
_14 _112 _1 _25 _39 _48 _1 _41 _1 _68
_16 _21 _1 _60 _12 _19 _14 _80 _1 _31
_1 _32 _27 _15 _10 _44 _1 _13 _10 _24
_1 _21 _1 _32 _8 _9 _1 _16 _1 _7
_6 _12 _1 _5 _1 _4 _1 _1 0 0
0 1 1 4 1 5 1 12 6 7
1 16 1 9 8 32 1 21 1 24
10 13 1 44 10 15 27 32 1 31
1 80 14 19 12 60 1 21 16 68
1 41 1 48 39 25 1 112 14 45
20 56 1 81 16 92 22 31 1 92
1 33 51 192 18 61 1 72 26 59
1 156 1 39 55 80 18 71 1 176
108 43 1 124 22 45 32 140 1 123
20 96 34 49 24 272 1 77 75 140

Also, it seems like it's worth verifying that order of evaluation does not create an ambiguity for the value of D:

   15 10 6 + 2 3 5 * D 15 10 6
31 31 31

Stretch task:

   (D 10x^1+i.4 5)%7
1 20 300 4000 50000
600000 7000000 80000000 900000000 10000000000
110000000000 1200000000000 13000000000000 140000000000000 1500000000000000
16000000000000000 170000000000000000 1800000000000000000 19000000000000000000 200000000000000000000

Julia[edit]

using Primes
 
D(n) = n < 0 ? -D(-n) : n < 2 ? zero(n) : isprime(n) ? one(n) : typeof(n)(sum(e * n ÷ p for (p, e) in eachfactor(n)))
 
foreach(p -> print(lpad(p[2], 5), p[1] % 10 == 0 ? "\n" : ""), pairs(map(D, -99:100)))
 
println()
for m in 1:20
println("D for 10^", rpad(m, 3), "divided by 7 is ", D(Int128(10)^m) ÷ 7)
end
 
Output:
  -75  -77   -1 -272  -24  -49  -34  -96  -20 -123
   -1 -140  -32  -45  -22 -124   -1  -43 -108 -176
   -1  -71  -18  -80  -55  -39   -1 -156   -1  -59
  -26  -72   -1  -61  -18 -192  -51  -33   -1  -92
   -1  -31  -22  -92  -16  -81   -1  -56  -20  -45
  -14 -112   -1  -25  -39  -48   -1  -41   -1  -68
  -16  -21   -1  -60  -12  -19  -14  -80   -1  -31
   -1  -32  -27  -15  -10  -44   -1  -13  -10  -24
   -1  -21   -1  -32   -8   -9   -1  -16   -1   -7
   -6  -12   -1   -5   -1   -4   -1   -1    0    0
    0    1    1    4    1    5    1   12    6    7
    1   16    1    9    8   32    1   21    1   24
   10   13    1   44   10   15   27   32    1   31
    1   80   14   19   12   60    1   21   16   68
    1   41    1   48   39   25    1  112   14   45
   20   56    1   81   16   92   22   31    1   92
    1   33   51  192   18   61    1   72   26   59
    1  156    1   39   55   80   18   71    1  176
  108   43    1  124   22   45   32  140    1  123
   20   96   34   49   24  272    1   77   75  140

D for 10^1  divided by 7 is 1
D for 10^2  divided by 7 is 20
D for 10^3  divided by 7 is 300
D for 10^4  divided by 7 is 4000
D for 10^5  divided by 7 is 50000
D for 10^6  divided by 7 is 600000
D for 10^7  divided by 7 is 7000000
D for 10^8  divided by 7 is 80000000
D for 10^9  divided by 7 is 900000000
D for 10^10 divided by 7 is 10000000000
D for 10^11 divided by 7 is 110000000000
D for 10^12 divided by 7 is 1200000000000
D for 10^13 divided by 7 is 13000000000000
D for 10^14 divided by 7 is 140000000000000
D for 10^15 divided by 7 is 1500000000000000
D for 10^16 divided by 7 is 16000000000000000
D for 10^17 divided by 7 is 170000000000000000
D for 10^18 divided by 7 is 1800000000000000000
D for 10^19 divided by 7 is 19000000000000000000
D for 10^20 divided by 7 is 200000000000000000000

Perl[edit]

Translation of: J
Library: ntheory
use v5.36;
use bigint;
no warnings 'uninitialized';
use List::Util 'max';
use ntheory 'factor';
 
sub table ($c, @V) { my $t = $c * (my $w = 2 + length max @V); ( sprintf( ('%'.$w.'d')x@V, @V) ) =~ s/.{1,$t}\K/\n/gr }
 
sub D ($n) {
my(%f, $s);
$f{$_}++ for factor max 1, my $nabs = abs $n;
map { $s += $nabs * $f{$_} / $_ } keys %f;
$n > 0 ? $s : -$s;
}
 
say table 10, map { D $_ } -99 .. 100;
say join "\n", map { sprintf('D(10**%-2d) / 7 == ', $_) . D(10**$_) / 7 } 1 .. 20;
 
Output:
  -75  -77   -1 -272  -24  -49  -34  -96  -20 -123
   -1 -140  -32  -45  -22 -124   -1  -43 -108 -176
   -1  -71  -18  -80  -55  -39   -1 -156   -1  -59
  -26  -72   -1  -61  -18 -192  -51  -33   -1  -92
   -1  -31  -22  -92  -16  -81   -1  -56  -20  -45
  -14 -112   -1  -25  -39  -48   -1  -41   -1  -68
  -16  -21   -1  -60  -12  -19  -14  -80   -1  -31
   -1  -32  -27  -15  -10  -44   -1  -13  -10  -24
   -1  -21   -1  -32   -8   -9   -1  -16   -1   -7
   -6  -12   -1   -5   -1   -4   -1   -1    0    0
    0    1    1    4    1    5    1   12    6    7
    1   16    1    9    8   32    1   21    1   24
   10   13    1   44   10   15   27   32    1   31
    1   80   14   19   12   60    1   21   16   68
    1   41    1   48   39   25    1  112   14   45
   20   56    1   81   16   92   22   31    1   92
    1   33   51  192   18   61    1   72   26   59
    1  156    1   39   55   80   18   71    1  176
  108   43    1  124   22   45   32  140    1  123
   20   96   34   49   24  272    1   77   75  140

D(10**1 ) / 7 == 1
D(10**2 ) / 7 == 20
D(10**3 ) / 7 == 300
D(10**4 ) / 7 == 4000
D(10**5 ) / 7 == 50000
D(10**6 ) / 7 == 600000
D(10**7 ) / 7 == 7000000
D(10**8 ) / 7 == 80000000
D(10**9 ) / 7 == 900000000
D(10**10) / 7 == 10000000000
D(10**11) / 7 == 110000000000
D(10**12) / 7 == 1200000000000
D(10**13) / 7 == 13000000000000
D(10**14) / 7 == 140000000000000
D(10**15) / 7 == 1500000000000000
D(10**16) / 7 == 16000000000000000
D(10**17) / 7 == 170000000000000000
D(10**18) / 7 == 1800000000000000000
D(10**19) / 7 == 19000000000000000000
D(10**20) / 7 == 200000000000000000000

Phix[edit]

with javascript_semantics
include mpfr.e
procedure D(mpz n)
    integer s = mpz_cmp_si(n,0)
    if s<0 then mpz_neg(n,n) end if
    if mpz_cmp_si(n,2)<0 then
        mpz_set_si(n,0)
    else
        sequence f = mpz_prime_factors(n)
        integer c = sum(vslice(f,2)),
                f1 = f[1][1]
        if c=1 then
            mpz_set_si(n,1)
        elsif c=2 then
            mpz_set_si(n,f1 + iff(length(f)=1?f1:f[2][1]))
        else
            assert(mpz_fdiv_q_ui(n,n,f1)=0)
            mpz d = mpz_init_set(n)
            D(n)
            mpz_mul_si(n,n,f1)
            mpz_add(n,n,d)
        end if
        if s<0 then mpz_neg(n,n) end if
    end if
end procedure
 
sequence res = repeat(0,200)
mpz n = mpz_init()
for i=-99 to 100 do
    mpz_set_si(n,i)
    D(n)
    res[i+100] = mpz_get_str(n)
end for
printf(1,"%s\n\n",{join_by(res,1,10," ",fmt:="%4s")})
for m=1 to 20 do
    mpz_ui_pow_ui(n,10,m)
    D(n)
    assert(mpz_fdiv_q_ui(n,n,7)=0)
    printf(1,"D(10^%d)/7 = %s\n",{m,mpz_get_str(n)})
end for
Output:
 -75  -77   -1 -272  -24  -49  -34  -96  -20 -123
  -1 -140  -32  -45  -22 -124   -1  -43 -108 -176
  -1  -71  -18  -80  -55  -39   -1 -156   -1  -59
 -26  -72   -1  -61  -18 -192  -51  -33   -1  -92
  -1  -31  -22  -92  -16  -81   -1  -56  -20  -45
 -14 -112   -1  -25  -39  -48   -1  -41   -1  -68
 -16  -21   -1  -60  -12  -19  -14  -80   -1  -31
  -1  -32  -27  -15  -10  -44   -1  -13  -10  -24
  -1  -21   -1  -32   -8   -9   -1  -16   -1   -7
  -6  -12   -1   -5   -1   -4   -1   -1    0    0
   0    1    1    4    1    5    1   12    6    7
   1   16    1    9    8   32    1   21    1   24
  10   13    1   44   10   15   27   32    1   31
   1   80   14   19   12   60    1   21   16   68
   1   41    1   48   39   25    1  112   14   45
  20   56    1   81   16   92   22   31    1   92
   1   33   51  192   18   61    1   72   26   59
   1  156    1   39   55   80   18   71    1  176
 108   43    1  124   22   45   32  140    1  123
  20   96   34   49   24  272    1   77   75  140

D(10^1)/7 = 1
D(10^2)/7 = 20
D(10^3)/7 = 300
D(10^4)/7 = 4000
D(10^5)/7 = 50000
D(10^6)/7 = 600000
D(10^7)/7 = 7000000
D(10^8)/7 = 80000000
D(10^9)/7 = 900000000
D(10^10)/7 = 10000000000
D(10^11)/7 = 110000000000
D(10^12)/7 = 1200000000000
D(10^13)/7 = 13000000000000
D(10^14)/7 = 140000000000000
D(10^15)/7 = 1500000000000000
D(10^16)/7 = 16000000000000000
D(10^17)/7 = 170000000000000000
D(10^18)/7 = 1800000000000000000
D(10^19)/7 = 19000000000000000000
D(10^20)/7 = 200000000000000000000

Python[edit]

from sympy.ntheory import factorint
 
def D(n):
if n < 0:
return -D(-n)
elif n < 2:
return 0
else:
fdict = factorint(n)
if len(fdict) == 1 and 1 in fdict: # is prime
return 1
return sum([n * e // p for p, e in fdict.items()])
 
for n in range(-99, 101):
print('{:5}'.format(D(n)), end='\n' if n % 10 == 0 else '')
 
print()
for m in range(1, 21):
print('(D for 10**{}) divided by 7 is {}'.format(m, D(10 ** m) // 7))
 
 
Output:
  -75  -77   -1 -272  -24  -49  -34  -96  -20 -123
   -1 -140  -32  -45  -22 -124   -1  -43 -108 -176
   -1  -71  -18  -80  -55  -39   -1 -156   -1  -59
  -26  -72   -1  -61  -18 -192  -51  -33   -1  -92
   -1  -31  -22  -92  -16  -81   -1  -56  -20  -45
  -14 -112   -1  -25  -39  -48   -1  -41   -1  -68
  -16  -21   -1  -60  -12  -19  -14  -80   -1  -31
   -1  -32  -27  -15  -10  -44   -1  -13  -10  -24
   -1  -21   -1  -32   -8   -9   -1  -16   -1   -7
   -6  -12   -1   -5   -1   -4   -1   -1    0    0
    0    1    1    4    1    5    1   12    6    7
    1   16    1    9    8   32    1   21    1   24
   10   13    1   44   10   15   27   32    1   31
    1   80   14   19   12   60    1   21   16   68
    1   41    1   48   39   25    1  112   14   45
   20   56    1   81   16   92   22   31    1   92
    1   33   51  192   18   61    1   72   26   59
    1  156    1   39   55   80   18   71    1  176
  108   43    1  124   22   45   32  140    1  123
   20   96   34   49   24  272    1   77   75  140

(D for 10**1) divided by 7 is 1
(D for 10**2) divided by 7 is 20
(D for 10**3) divided by 7 is 300
(D for 10**4) divided by 7 is 4000
(D for 10**5) divided by 7 is 50000
(D for 10**6) divided by 7 is 600000
(D for 10**7) divided by 7 is 7000000
(D for 10**8) divided by 7 is 80000000
(D for 10**9) divided by 7 is 900000000
(D for 10**10) divided by 7 is 10000000000
(D for 10**11) divided by 7 is 110000000000
(D for 10**12) divided by 7 is 1200000000000
(D for 10**13) divided by 7 is 13000000000000
(D for 10**14) divided by 7 is 140000000000000
(D for 10**15) divided by 7 is 1500000000000000
(D for 10**16) divided by 7 is 16000000000000000
(D for 10**17) divided by 7 is 170000000000000000
(D for 10**18) divided by 7 is 1800000000000000000
(D for 10**19) divided by 7 is 19000000000000000000
(D for 10**20) divided by 7 is 200000000000000000000

Raku[edit]

use Prime::Factor;
 
multi D (0) { 0 }
multi D (1) { 0 }
multi D ($n where &is-prime) { 1 }
multi D ($n where * < 0 ) { -D -$n }
multi D ($n) { sum $n.&prime-factors.Bag.map: { $n × .value / .key } }
 
 
put (-99 .. 100).map(&D).batch(10)».fmt("%4d").join: "\n";
 
put '';
 
put join "\n", (1..20).map: { sprintf "D(10**%-2d) / 7 == %d", $_, D(10**$_) / 7 }
Output:
 -75  -77   -1 -272  -24  -49  -34  -96  -20 -123
  -1 -140  -32  -45  -22 -124   -1  -43 -108 -176
  -1  -71  -18  -80  -55  -39   -1 -156   -1  -59
 -26  -72   -1  -61  -18 -192  -51  -33   -1  -92
  -1  -31  -22  -92  -16  -81   -1  -56  -20  -45
 -14 -112   -1  -25  -39  -48   -1  -41   -1  -68
 -16  -21   -1  -60  -12  -19  -14  -80   -1  -31
  -1  -32  -27  -15  -10  -44   -1  -13  -10  -24
  -1  -21   -1  -32   -8   -9   -1  -16   -1   -7
  -6  -12   -1   -5   -1   -4   -1   -1    0    0
   0    1    1    4    1    5    1   12    6    7
   1   16    1    9    8   32    1   21    1   24
  10   13    1   44   10   15   27   32    1   31
   1   80   14   19   12   60    1   21   16   68
   1   41    1   48   39   25    1  112   14   45
  20   56    1   81   16   92   22   31    1   92
   1   33   51  192   18   61    1   72   26   59
   1  156    1   39   55   80   18   71    1  176
 108   43    1  124   22   45   32  140    1  123
  20   96   34   49   24  272    1   77   75  140

D(10**1 ) / 7 == 1
D(10**2 ) / 7 == 20
D(10**3 ) / 7 == 300
D(10**4 ) / 7 == 4000
D(10**5 ) / 7 == 50000
D(10**6 ) / 7 == 600000
D(10**7 ) / 7 == 7000000
D(10**8 ) / 7 == 80000000
D(10**9 ) / 7 == 900000000
D(10**10) / 7 == 10000000000
D(10**11) / 7 == 110000000000
D(10**12) / 7 == 1200000000000
D(10**13) / 7 == 13000000000000
D(10**14) / 7 == 140000000000000
D(10**15) / 7 == 1500000000000000
D(10**16) / 7 == 16000000000000000
D(10**17) / 7 == 170000000000000000
D(10**18) / 7 == 1800000000000000000
D(10**19) / 7 == 19000000000000000000
D(10**20) / 7 == 200000000000000000000

Wren[edit]

Library: Wren-big
Library: Wren-fmt

As integer arithmetic in Wren is inaccurate above 2^53 we need to use BigInt here.

import "./big" for BigInt
import "./fmt" for Fmt
 
var D = Fn.new { |n|
if (n < 0) return -D.call(-n)
if (n < 2) return BigInt.zero
var f = BigInt.primeFactors(n)
var c = f.count
if (c == 1) return BigInt.one
if (c == 2) return f[0] + f[1]
var d = n / f[0]
return D.call(d) * f[0] + d
}
 
var ad = List.filled(200, 0)
for (n in -99..100) ad[n+99] = D.call(BigInt.new(n))
Fmt.tprint("$4i", ad, 10)
System.print()
for (m in 1..20) {
Fmt.print("D(10^$-2d) / 7 = $i", m, D.call(BigInt.ten.pow(m))/7)
}
Output:
 -75  -77   -1 -272  -24  -49  -34  -96  -20 -123 
  -1 -140  -32  -45  -22 -124   -1  -43 -108 -176 
  -1  -71  -18  -80  -55  -39   -1 -156   -1  -59 
 -26  -72   -1  -61  -18 -192  -51  -33   -1  -92 
  -1  -31  -22  -92  -16  -81   -1  -56  -20  -45 
 -14 -112   -1  -25  -39  -48   -1  -41   -1  -68 
 -16  -21   -1  -60  -12  -19  -14  -80   -1  -31 
  -1  -32  -27  -15  -10  -44   -1  -13  -10  -24 
  -1  -21   -1  -32   -8   -9   -1  -16   -1   -7 
  -6  -12   -1   -5   -1   -4   -1   -1    0    0 
   0    1    1    4    1    5    1   12    6    7 
   1   16    1    9    8   32    1   21    1   24 
  10   13    1   44   10   15   27   32    1   31 
   1   80   14   19   12   60    1   21   16   68 
   1   41    1   48   39   25    1  112   14   45 
  20   56    1   81   16   92   22   31    1   92 
   1   33   51  192   18   61    1   72   26   59 
   1  156    1   39   55   80   18   71    1  176 
 108   43    1  124   22   45   32  140    1  123 
  20   96   34   49   24  272    1   77   75  140 

D(10^1 ) / 7 = 1
D(10^2 ) / 7 = 20
D(10^3 ) / 7 = 300
D(10^4 ) / 7 = 4000
D(10^5 ) / 7 = 50000
D(10^6 ) / 7 = 600000
D(10^7 ) / 7 = 7000000
D(10^8 ) / 7 = 80000000
D(10^9 ) / 7 = 900000000
D(10^10) / 7 = 10000000000
D(10^11) / 7 = 110000000000
D(10^12) / 7 = 1200000000000
D(10^13) / 7 = 13000000000000
D(10^14) / 7 = 140000000000000
D(10^15) / 7 = 1500000000000000
D(10^16) / 7 = 16000000000000000
D(10^17) / 7 = 170000000000000000
D(10^18) / 7 = 1800000000000000000
D(10^19) / 7 = 19000000000000000000
D(10^20) / 7 = 200000000000000000000