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 A280101 #25 Dec 12 2023 18:32:35 %S A280101 1,1,4,7,12,15,28,60,91,195,252,360,252,216,744,896,1020,1512,1651, %T A280101 2400,3048,7644,6552,4800,6720,10890,24384,19812,17360,20160,45136, %U A280101 35280,40320,54600,78624,68400,27540,79248,115200,219583,265980,200312,268800,335160 %N A280101 a(n) = sigma(sigma(p(n))) = sum of the divisors of the sum of the divisors of number of partitions of n. %H A280101 Daniel Suteu, <a href="/A280101/b280101.txt">Table of n, a(n) for n = 0..3000</a> %F A280101 a(n) = A000203(A000203(A000041(n))) = A051027(A000041(n)). %F A280101 a(n) = A000203(A139041(n)), n >= 1. %e A280101 For n = 7 the number of partitions of 7 is p(7) = 15, and the sum of the divisors of 15 is sigma(15) = 1 + 3 + 5 + 15 = 24, and the sum of the divisors of 24 is sigma(24) = 1 + 2 + 3 + 4 + 6 + 8 + 12 + 24 = 60, so a(7) = 60. %t A280101 Array[DivisorSigma[1, DivisorSigma[1, PartitionsP[#]]]&, 43, 0] (* _Amiram Eldar_, Feb 19 2019 *) %o A280101 (PARI) a(n) = sigma(sigma(numbpart(n))); \\ _Michel Marcus_, Feb 19 2019 %Y A280101 Cf. A000041, A000203, A051027, A139041. %K A280101 nonn %O A280101 0,3 %A A280101 _Omar E. Pol_, Dec 25 2016