cp's OEIS Frontend

A326146 a(n) = sigma(n) - A020639(n) - n, where A020639 gives the smallest prime factor of n, and sigma is the sum of divisors of n.

%I A326146 #9 Jun 12 2019 19:14:28
%S A326146 -1,-1,-2,1,-4,4,-6,5,1,6,-10,14,-12,8,6,13,-16,19,-18,20,8,12,-22,34,
%T A326146 1,14,10,26,-28,40,-30,29,12,18,8,53,-36,20,14,48,-40,52,-42,38,30,24,
%U A326146 -46,74,1,41,18,44,-52,64,12,62,20,30,-58,106,-60,32,38,61,14,76,-66,56,24,72,-70,121,-72,38,46,62,12,88
%N A326146 a(n) = sigma(n) - A020639(n) - n, where A020639 gives the smallest prime factor of n, and sigma is the sum of divisors of n.
%H A326146 Antti Karttunen, <a href="/A326146/b326146.txt">Table of n, a(n) for n = 1..20000</a>
%F A326146 a(n) = A000203(n) - A020639(n) - n = A000203(n) - A061228(n).
%F A326146 a(n) = A001065(n) - A020639(n).
%F A326146 For n > 1, a(n) = A105086(n) - n.
%o A326146 (PARI)
%o A326146 A020639(n) = if(1==n, n, factor(n)[1, 1]);
%o A326146 A326146(n) = (sigma(n)-A020639(n)-n);
%Y A326146 Cf. A000203, A001065, A020639, A061228, A105086, A326074, A326147, A326148.
%K A326146 sign
%O A326146 1,3
%A A326146 _Antti Karttunen_, Jun 10 2019