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 A384727 #17 Jun 10 2025 02:20:25 %S A384727 1,1,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0, %T A384727 0,1,0,0,0,2,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0, %U A384727 0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1 %N A384727 Number of groups of order n (up to isomorphism) with exactly n subgroups. %C A384727 See A384800 for more information. %H A384727 Richard Stanley, <a href="/A384727/b384727.txt">Table of n, a(n) for n = 1..192</a> %H A384727 Richard Stanley, <a href="https://mathoverflow.net/questions/495845">What finite groups have as many elements as subgroups?</a> Question in Mathoverflow, answered by Dave Benson and others, Jun 07 2025. %e A384727 The symmetric group S_3 has six elements and six subgroups. The other group of order six has four subgroups, so a(6)=1. %Y A384727 Cf. A368538, A384800. %K A384727 nonn %O A384727 1,40 %A A384727 _Richard Stanley_, Jun 08 2025