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 A356456 #11 Aug 08 2022 09:15:43 %S A356456 10,28,40,50,70,77,110,130,133,136,140,154,155,160,161,170,176,190, %T A356456 196,200,209,224,230,250,259,266,275,280,290,308,310,322,350,364,370, %U A356456 371,377,385,410,416,418,430,440,469,470,476,490,496,518,520,530,532,539,550,553,590 %N A356456 Numbers k not divisible by 3 such that 2*k^2 is not in A014567. %C A356456 Numbers k not divisible by 3 such that k and sigma(2*k^2) are not coprime, sigma = A000203. %C A356456 Note that if m is twice a square, then sigma(m) is divisible by 3 (cf. A065766). %H A356456 Jianing Song, <a href="/A356456/b356456.txt">Table of n, a(n) for n = 1..11669</a> (all terms <= 100000) %e A356456 28 is a term since 28 and sigma(2*28^2) = 3591 have a common factor 7, and 28 is not divisible by 3. %o A356456 (PARI) isA356456(n) = (n%3) && gcd(n, sigma(2*n^2))>1 %Y A356456 Cf. A014567, A000203, A065766. %Y A356456 Equals A356453 \ A008585. %K A356456 nonn,easy %O A356456 1,1 %A A356456 _Jianing Song_, Aug 07 2022