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 A202276 #17 Dec 20 2024 02:41:07
%S A202276 0,1,1,1,2,2,2,2,3,4,5,5,5,5,5,6,7,7,8,8,9,10,11,11,12,13,14,14,15,15,
%T A202276 15,15,16,17,18,18,19,19,19,19,20,20,21,21,22,23,24,24,25,26,27,28,29,
%U A202276 29,30,30,30,31,32,32,33,33,33,34,35,36,37,37,38,39
%N A202276 Number of integers k <= n such that sigma(x) = k has no solution, sigma = A000203.
%C A202276 Partial sums of A175253.
%H A202276 Jaroslav Krizek, <a href="/A202276/b202276.txt">Table of n, a(n) for n = 1..10000</a>
%e A202276 a(9) = 3 because sigma(x) = k has no solution for k = 2, 5 and 9.
%t A202276 seq[max_] := Module[{t = Table[0, {max}]}, t[[Complement[Range[max], Table[ DivisorSigma[1, n], {n, 1, max}]]]] = 1; Accumulate@ t]; seq[100] (* _Amiram Eldar_, Dec 20 2024 *)
%Y A202276 Cf. A074753, A202277, A202275, A175523, A007369, A007368, A007609.
%K A202276 nonn
%O A202276 1,5
%A A202276 _Jaroslav Krizek_, Dec 25 2011