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 A144613 #22 Aug 17 2025 18:01:20
%S A144613 4,12,13,28,24,39,32,60,40,72,48,91,56,96,78,124,72,120,80,168,104,
%T A144613 144,96,195,124,168,121,224,120,234,128,252,156,216,192,280,152,240,
%U A144613 182,360,168,312,176,336,240,288,192,403,228,372,234,392,216,363,288,480,260,360
%N A144613 a(n) = sigma(3*n) = A000203(3*n).
%H A144613 Seiichi Manyama, <a href="/A144613/b144613.txt">Table of n, a(n) for n = 1..10000</a>
%F A144613 a(n) = A000203(n) + 3*A078708(n). - _R. J. Mathar_, May 19 2020
%F A144613 Sum_{k=1..n} a(k) = (11*Pi^2/36) * n^2 + O(n*log(n)). - _Amiram Eldar_, Dec 16 2022
%t A144613 a[n_] := DivisorSigma[1, 3*n]; Array[a, 60] (* _Amiram Eldar_, Dec 16 2022 *)
%o A144613 (PARI) vector(66, n, sigma(3*n, 1)) \\ _Joerg Arndt_, Jul 30 2011
%Y A144613 Sigma(k*n): A000203 (k=1), A062731 (k=2), this sequence (k=3), A193553 (k=4), A283118 (k=5), A224613 (k=6), A283078 (k=7), A283122 (k=8), A283123 (k=9).
%Y A144613 Cf. A008585, A078708.
%K A144613 nonn,easy,changed
%O A144613 1,1
%A A144613 _N. J. A. Sloane_, Jan 15 2009
%E A144613 Zero removed and offset corrected by _Seiichi Manyama_, Feb 28 2017