Blum integer: Difference between revisions

=={{header|Nim}}==

{{trans|Wren}}

<syntaxhighlight lang="Nim">import std/[strformat, tables]

func isPrime(n: Natural): bool =

## Return "true" is "n" is prime.

if n < 2: return false

if (n and 1) == 0: return n == 2

if n mod 3 == 0: return n == 3

var d = 5

var step = 2

while d * d <= n:

if n mod d == 0:

return false

inc d, step

step = 6 - step

return true

const Inc = [4, 2, 4, 2, 4, 6, 2, 6]

func firstPrimeFactor(n: Positive): int =

## Return the first prime factor.

## Assuming "n" is odd.

if n == 1: return 1

if n mod 3 == 0: return 3

if n mod 5 == 0: return 5

var k = 7

var i = 0

while k * k <= n:

if n mod k == 0:

return k

k += Inc[i]

i = (i + 1) and 7

return n

var blum = newSeq[int](50)

var bc = 0

var counts: CountTable[int]

var n = 1

while true:

var p = n.firstPrimeFactor

if (p and 3) == 3:

let q = n div p

if q != p and (q and 3) == 3 and q.isPrime:

if bc < 50: blum[bc] = n

counts.inc(n mod 10)

inc bc

if bc == 50:

echo "First 50 Blum integers:"

for i, val in blum:

stdout.write &"{val:3}"

stdout.write if i mod 10 == 9: '\n' else: ' '

echo()

elif bc == 26828 or bc mod 100000 == 0:

echo &"The {bc:>6}th Blum integer is: {n:>7}"

if bc == 400000:

echo "\n% distribution of the first 400_000 Blum integers:"

for i in [1, 3, 7, 9]:

echo &" {counts[i]/4000:6.5} % end in {i}"

break

n = if n mod 5 == 3: n + 4 else: n + 2

</syntaxhighlight>

{{out}}

<pre>First 50 Blum integers:

21 33 57 69 77 93 129 133 141 161

177 201 209 213 217 237 249 253 301 309

321 329 341 381 393 413 417 437 453 469

473 489 497 501 517 537 553 573 581 589

597 633 649 669 681 713 717 721 737 749

The 26828th Blum integer is: 524273

The 100000th Blum integer is: 2075217

The 200000th Blum integer is: 4275533

The 300000th Blum integer is: 6521629

The 400000th Blum integer is: 8802377

% distribution of the first 400_000 Blum integers:

25.001 % end in 1

25.017 % end in 3

24.997 % end in 7

24.985 % end in 9

</pre>