cp's OEIS Frontend

A379479 Numbers k such that the greatest common divisor of k, sigma(k) and A003961(k) is 1 and gcd(A003961(k)-2k, A003961(k)-sigma(k)) > 1.

%I A379479 #11 Dec 23 2024 17:48:55
%S A379479 7,13,19,28,31,37,43,46,55,61,67,68,69,79,91,97,103,106,109,127,131,
%T A379479 139,146,151,163,166,175,181,193,199,200,223,229,241,251,261,271,277,
%U A379479 283,301,307,313,323,325,331,337,344,346,349,371,379,391,397,409,421,428,439,444,449,457,463,466,475,481,487,491,494,496
%N A379479 Numbers k such that the greatest common divisor of k, sigma(k) and A003961(k) is 1 and gcd(A003961(k)-2k, A003961(k)-sigma(k)) > 1.
%C A379479 Not a subsequence of A319630. Terms 175, 323, 444, 847, 874, 1095, 1147, 1236, 1400, 1573, 1768, 1884, 2001, ... are instead in A104210.
%H A379479 Antti Karttunen, <a href="/A379479/b379479.txt">Table of n, a(n) for n = 1..20000</a>
%H A379479 <a href="/index/Pri#prime_indices">Index entries for sequences related to prime indices in the factorization of n</a>.
%H A379479 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A379479 {k such that A372565(k) = 1 and A326057(k) > 1}.
%e A379479 7 is included as the greatest common divisor of 7, 8 and 9 is 1, but the greatest common divisor of 11-14 and 11-8 is 3 > 1.
%e A379479 28 is included as the greatest common divisor of 28, 56 and 99 is 1, but gcd(99-56,99-56) = 43 > 1.
%o A379479 (PARI) is_A379479 = A379478;
%Y A379479 Setwise difference A379477 \ A372566.
%Y A379479 Cf. A000203, A003961, A326057, A372565, A379478 (characteristic function).
%Y A379479 Cf. A000396 (at least the even terms > 6 form a subsequence of this sequence).
%Y A379479 Cf. also A104210, A319630.
%K A379479 nonn
%O A379479 1,1
%A A379479 _Antti Karttunen_, Dec 23 2024