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 A284210 #18 Mar 06 2025 10:15:41 %S A284210 1,1,1,7,6,280,120,25335,11200,276696,362880,374838255,39916800, %T A284210 2414617920,11721790080 %N A284210 Number of subgroups of order n of the symmetric group Sym(n) on n symbols. %C A284210 The diagonal of A243748. - _R. J. Mathar_, Mar 30 2017 [edited by _Peter Munn_, Mar 06 2025] %F A284210 If n is prime, A284210(n) = (n-2)!. %e A284210 The group Sym(4) contains 3 cyclic groups of order 4, 3 non-normal elementary abelian groups of order 4 and one normal group of order 4, so A284210(4) = 3 + 3 + 1 = 7. %o A284210 (GAP) List([1..14], n -> Sum(List(Filtered(ConjugacyClassesSubgroups(SymmetricGroup(n)), c -> Size(Representative(c)) = n)), c -> Size(c))); %K A284210 nonn,more %O A284210 1,4 %A A284210 _Jens Voß_, Mar 23 2017