Chowla numbers: Difference between revisions
Add PARI/GP implementation
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There are 5 perfect numbers < 350,000,000
</pre>
=={{header|PARI/GP}}==
{{trans|Julia}}
<syntaxhighlight lang="PARI/GP">
chowla(n) = {
if (n < 1, error("Chowla function argument must be positive"));
if (n < 4, return(0));
my(divs = divisors(n));
sum(i=1, #divs, divs[i]) - n - 1;
}
\\ Function to count Chowla numbers
countchowlas(n, asperfect = 1, verbose = 1) = {
my(count = 0, chow, i);
for (i = 2, n,
chow = chowla(i);
if ( (asperfect && (chow == i - 1)) || ((!asperfect) && (chow == 0)),
count++;
if (verbose, print("The number " i " is " if (asperfect, "perfect.", "prime.")));
);
);
count;
}
\\ Main execution block
{
print("The first 37 chowla numbers are:");
for (i = 1, 37, printf("Chowla(%s) is %s\n", Str(i), Str(chowla(i)) ) );
m=100;
while(m<=10000000, print("The count of the primes up to " m " is " countchowlas(m, 0, 0)); m=m*10);
print("The count of perfect numbers up to 35,000,000 is " countchowlas(35000000, 1, 1));
}
</syntaxhighlight>
{{out}}
<pre>
The first 37 chowla numbers are:
Chowla(1) is 0
Chowla(2) is 0
Chowla(3) is 0
Chowla(4) is 2
Chowla(5) is 0
Chowla(6) is 5
Chowla(7) is 0
Chowla(8) is 6
Chowla(9) is 3
Chowla(10) is 7
Chowla(11) is 0
Chowla(12) is 15
Chowla(13) is 0
Chowla(14) is 9
Chowla(15) is 8
Chowla(16) is 14
Chowla(17) is 0
Chowla(18) is 20
Chowla(19) is 0
Chowla(20) is 21
Chowla(21) is 10
Chowla(22) is 13
Chowla(23) is 0
Chowla(24) is 35
Chowla(25) is 5
Chowla(26) is 15
Chowla(27) is 12
Chowla(28) is 27
Chowla(29) is 0
Chowla(30) is 41
Chowla(31) is 0
Chowla(32) is 30
Chowla(33) is 14
Chowla(34) is 19
Chowla(35) is 12
Chowla(36) is 54
Chowla(37) is 0
The count of the primes up to 100 is 25
The count of the primes up to 1000 is 168
The count of the primes up to 10000 is 1229
The count of the primes up to 100000 is 9592
The count of the primes up to 1000000 is 78498
The count of the primes up to 10000000 is 664579
The number 6 is perfect.
The number 28 is perfect.
The number 496 is perfect.
The number 8128 is perfect.
The number 33550336 is perfect.
The count of perfect numbers up to 35000000 is 5.
</pre>
=={{header|Pascal}}==
{{works with|Free Pascal}}
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