Erdős-Nicolas numbers: Difference between revisions
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slight improvement version
User time: 0.139 s CPU share: 98.80 %
</pre>
=={{header|C#}}==
{{trans|Java}}
<syntaxhighlight lang="C#">
using System;
class ErdosNicolasNumbers
{
static void Main(string[] args)
{
const int limit = 100_000_000;
int[] divisorSum = new int[limit + 1];
int[] divisorCount = new int[limit + 1];
for (int i = 0; i <= limit; i++)
{
divisorSum[i] = 1;
divisorCount[i] = 1;
}
for (int index = 2; index <= limit / 2; index++)
{
for (int number = 2 * index; number <= limit; number += index)
{
if (divisorSum[number] == number)
{
Console.WriteLine($"{number,8} equals the sum of its first {divisorCount[number],3} divisors");
}
divisorSum[number] += index;
divisorCount[number]++;
}
}
}
}
</syntaxhighlight>
{{out}}
<pre>
24 equals the sum of its first 6 divisors
2016 equals the sum of its first 31 divisors
8190 equals the sum of its first 43 divisors
42336 equals the sum of its first 66 divisors
45864 equals the sum of its first 66 divisors
714240 equals the sum of its first 113 divisors
392448 equals the sum of its first 68 divisors
1571328 equals the sum of its first 115 divisors
61900800 equals the sum of its first 280 divisors
91963648 equals the sum of its first 142 divisors
</pre>
Line 454 ⟶ 503:
91963648 equals the sum of its first 142 divisors
</pre>
=={{header|EasyLang}}==
{{trans|FreeBASIC}}
<syntaxhighlight>
limit = 2000000
for i to limit
dsum[] &= 1
dcnt[] &= 1
.
for i = 2 to limit
j = i + i
while j <= limit
if dsum[j] = j
print j & " equals the sum of its first " & dcnt[j] & " divisors"
.
dsum[j] += i
dcnt[j] += 1
j += i
.
.
</syntaxhighlight>
=={{header|FutureBasic}}==
Line 1,115 ⟶ 1,185:
foreach my $d (divisors($n)) {
++$count; $sum += $d;
return False if ($sum > $n);
}
}
Line 1,170 ⟶ 1,237:
Output same as Julia
=={{header|Python}}==
{{trans|C}}
This is a translation of the "slight improvement" C code. I ran this script using PyPy7.3.13 (Python3.10.13) and it completes in ~10.5s on a AMD Ryzen 7 7800X3D.
<syntaxhighlight lang="python">
# erdos-nicolas.py by Xing216
from time import perf_counter
start = perf_counter()
def get_div_cnt(n: int) -> None:
divcnt,divsum = 1,1
lmt = n/2
f = 2
while True:
if f > lmt: break
if not (n % f):
divsum += f
divcnt += 1
if divsum == n: break
f+=1
print(f"{n:>8} equals the sum of its first {divcnt} divisors")
max_number = 91963649
dsum = [1 for _ in range(max_number+1)]
for i in range(2, max_number + 1):
for j in range(i + i, max_number + 1, i):
if (dsum[j] == j): get_div_cnt(j)
dsum[j] += i
done = perf_counter() - start
print(f"Done in: {done:.3f}s")
</syntaxhighlight>
{{out}}
<pre>
24 equals the sum of its first 6 divisors
2016 equals the sum of its first 31 divisors
8190 equals the sum of its first 43 divisors
42336 equals the sum of its first 66 divisors
45864 equals the sum of its first 66 divisors
714240 equals the sum of its first 113 divisors
392448 equals the sum of its first 68 divisors
1571328 equals the sum of its first 115 divisors
61900800 equals the sum of its first 280 divisors
91963648 equals the sum of its first 142 divisors
Done in: 10.478s
</pre>
=={{header|Raku}}==
<syntaxhighlight lang="raku" line>use Prime::Factor;
Line 1,236 ⟶ 1,345:
392448 equals the sum of its first 68 divisors
1571328 equals the sum of its first 115 divisors
</pre>
=={{header|Sidef}}==
<syntaxhighlight lang="ruby">func is_Erdős_Nicolas(n) {
n.is_abundant || return false
var sum = 0
var count = 0
n.divisors.each {|d|
++count; sum += d
return count if (sum == n)
return false if (sum > n)
}
}
var count = 8 # how many terms to compute
^Inf -> by(2).each {|n|
if (is_Erdős_Nicolas(n)) { |v|
say "#{'%8s'%n} is the sum of its first #{'%3s'%v} divisors"
--count || break
}
}</syntaxhighlight>
{{out}}
<pre>
24 is the sum of its first 6 divisors
2016 is the sum of its first 31 divisors
8190 is the sum of its first 43 divisors
42336 is the sum of its first 66 divisors
45864 is the sum of its first 66 divisors
392448 is the sum of its first 68 divisors
714240 is the sum of its first 113 divisors
1571328 is the sum of its first 115 divisors
</pre>
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