Perfect numbers: Difference between revisions
→Using built-in method
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=={{header|PARI/GP}}==
===Using built-in
<syntaxhighlight lang="parigp">
isPerfect(n)=sigma(n,-1)==2
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Show perfect numbers
<syntaxhighlight lang="parigp">
forprime(p=2, 2281,
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print(p"\t",(2^p-1)*2^(p-1))))
</syntaxhighlight>
faster alternative showing them still using built-in methods
<syntaxhighlight lang="parigp">
[n|n<-[1..10^4],sigma(n,-1)==2]
</syntaxhighlight>
===Faster with Lucas-Lehmer test===
<syntaxhighlight lang="parigp">p=2;n=3;n1=2;
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