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 A363890 #18 Jun 27 2023 09:17:03
%S A363890 2,5,10,11,16,17,27,23,28,29,42,40,40,41,57,47,57,53,80,59,64,70,87,
%T A363890 71,76,88,115,83,88,89,117,100,114,101,140,107,128,113,147,136,124,
%U A363890 130,170,131,136,137,216,154,148,149,200,160,160,184,207,167,194,173,241,179,224,190,237
%N A363890 Sum of divisors of 3*n-1 of form 3*k+2.
%H A363890 Seiichi Manyama, <a href="/A363890/b363890.txt">Table of n, a(n) for n = 1..10000</a>
%F A363890 a(n) = A078182(3*n-1).
%F A363890 G.f.: Sum_{k>0} (3*k-1) * x^k/(1 - x^(3*k-1)).
%t A363890 a[n_] := DivisorSum[3*n - 1, # &, Mod[#, 3] == 2 &]; Array[a, 100] (* _Amiram Eldar_, Jun 26 2023 *)
%o A363890 (PARI) a(n) = sumdiv(3*n-1, d, (d%3==2)*d);
%Y A363890 Cf. A363514, A363889, A363891.
%Y A363890 Cf. A078182, A359211.
%K A363890 nonn
%O A363890 1,1
%A A363890 _Seiichi Manyama_, Jun 26 2023