cp's OEIS Frontend

A379477 Numbers k such that A003961(k)-2k and A003961(k)-sigma(k) have a common divisor > 1, where A003961 is fully multiplicative with a(prime(i)) = prime(i+1), and sigma is the sum of divisors function.

%I A379477 #17 Dec 23 2024 17:48:47
%S A379477 6,7,13,18,19,24,28,30,31,37,42,43,46,54,55,60,61,66,67,68,69,72,78,
%T A379477 79,90,91,96,97,102,103,106,109,114,120,126,127,131,132,135,138,139,
%U A379477 140,146,150,151,162,163,166,168,174,175,180,181,186,193,198,199,200,204,210,216,222,223,229,234,240,241,246,251
%N A379477 Numbers k such that A003961(k)-2k and A003961(k)-sigma(k) have a common divisor > 1, where A003961 is fully multiplicative with a(prime(i)) = prime(i+1), and sigma is the sum of divisors function.
%H A379477 Antti Karttunen, <a href="/A379477/b379477.txt">Table of n, a(n) for n = 1..20000</a>
%H A379477 <a href="/index/O#opnseqs">Index entries for sequences where odd perfect numbers must occur, if they exist at all</a>
%H A379477 <a href="/index/Pri#prime_indices">Index entries for sequences related to prime indices in the factorization of n</a>.
%H A379477 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A379477 {k such that gcd(A252748(k), A286385(k)) > 1}.
%o A379477 (PARI) is_A379477 = A379476;
%Y A379477 Cf. A000203, A003961, A252748, A286385, A379476 (characteristic function).
%Y A379477 Positions of terms > 1 in A326057.
%Y A379477 Disjoint union of A372566 and A379479.
%Y A379477 Subsequences: A000396. See also A378980.
%K A379477 nonn
%O A379477 1,1
%A A379477 _Antti Karttunen_, Dec 23 2024