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%I #6 Mar 29 2019 21:08:34
%S 1,1,3,1,5,3,7,8,1,5,11,3,13,7,15,1,17,1,19,5,21,11,23,24,1,13,27,7,
%T 29,15,31,32,33,17,35,1,37,19,39,40,41,21,43,11,5,23,47,3,49,1,51,13,
%U 53,27,55,56,57,29,59,15,61,31,7,1,65,33,67,17,69,35,71,8,73,37,3,19,77,39,79,5,81,41,83,21,85,43,87,88,89,5,91
%N Multiplicative with a(p^e) = p^e if sigma(p^e) is composite, and 1 otherwise.
%H Antti Karttunen, <a href="/A324894/b324894.txt">Table of n, a(n) for n = 1..20000</a>
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F Multiplicative with a(p^e) = p^e if (p^(1+e) - 1)/(p-1) = 1 + p + p^2 + ... + p^e is composite, and 1 otherwise.
%F a(n) = n / A324892(n).
%e For n = 150 = 2 * 3 * 5^2, sigma(2) = 3 is prime, sigma(3) = 4 is not prime, and sigma(25) = 31 is prime, thus a(150) = 3.
%o (PARI) A324894(n) = { my(f=factor(n)); prod(i=1, #f~, (f[i,1]^!isprime(sigma(f[i,1]^f[i,2])))^f[i,2]); };
%Y Cf. A000203, A010051, A324892.
%K nonn,mult
%O 1,3
%A _Antti Karttunen_, Mar 29 2019
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