This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A324892 #8 Mar 29 2019 21:08:26
%S A324892 1,2,1,4,1,2,1,1,9,2,1,4,1,2,1,16,1,18,1,4,1,2,1,1,25,2,1,4,1,2,1,1,1,
%T A324892 2,1,36,1,2,1,1,1,2,1,4,9,2,1,16,1,50,1,4,1,2,1,1,1,2,1,4,1,2,9,64,1,
%U A324892 2,1,4,1,2,1,9,1,2,25,4,1,2,1,16,1,2,1,4,1,2,1,1,1,18,1,4,1,2,1,1,1,2,9,100,1,2,1,1,1
%N A324892 Multiplicative with a(p^e) = p^e if sigma(p^e) is prime, and 1 otherwise.
%H A324892 Antti Karttunen, <a href="/A324892/b324892.txt">Table of n, a(n) for n = 1..65537</a>
%H A324892 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A324892 Multiplicative with a(p^e) = p^e if (p^(1+e) - 1)/(p-1) = 1 + p + p^2 + ... + p^e is prime, and 1 otherwise.
%F A324892 a(n) = n / A324894(n).
%e A324892 For n = 150 = 2 * 3 * 5^2, sigma(2) = 3 is a prime, sigma(3) = 4 is not prime, and sigma(25) = 31 is a prime, thus a(150) = 2 * 25 = 50.
%o A324892 (PARI) A324892(n) = { my(f=factor(n)); prod(i=1, #f~, (f[i,1]^isprime(sigma(f[i,1]^f[i,2])))^f[i,2]); };
%o A324892 (PARI) A324892(n) = { my(f=factor(n)); prod(i=1, #f~, if(isprime(((f[i,1]^(1+f[i,2]))-1)/(f[i,1]-1)), f[i,1]^f[i,2], 1)); };
%Y A324892 Cf. A000203, A010051, A324894.
%K A324892 nonn,mult
%O A324892 1,2
%A A324892 _Antti Karttunen_, Mar 29 2019