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 A347878 #10 Sep 19 2021 22:02:06 %S A347878 1,3,6,7,8,11,12,14,15,18,19,21,22,23,24,27,28,30,31,33,35,36,38,39, %T A347878 42,43,44,46,47,48,49,50,51,54,55,56,57,59,60,62,63,65,66,67,69,70,71, %U A347878 75,76,77,78,79,81,83,84,85,86,87,88,91,92,93,94,95,96,99,100,102,103,105,107,108,110,111,112,114,115 %N A347878 Numbers k for which A003415(sigma(k)) is even. %C A347878 Numbers k such that A342925(k) == 0 (mod 2). %C A347878 Odd squares present are terms of A347886 squared. %C A347878 Conjecture: A342923 is a subsequence of this sequence. See comments in A347870. %t A347878 ad[1] = 0; ad[n_] := n * Total@(Last[#]/First[#]& /@ FactorInteger[n]); Select[Range[115], EvenQ[ad[DivisorSigma[1, #]]] &] (* _Amiram Eldar_, Sep 19 2021 *) %o A347878 (PARI) isA347878(n) = !A347870(n); %Y A347878 Cf. A000203, A003415, A342923, A342925, A347872, A347873, A347877 (complement), A347886. %Y A347878 Positions of zeros in A347870. %K A347878 nonn %O A347878 1,2 %A A347878 _Antti Karttunen_, Sep 19 2021