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 A181964 #11 Apr 05 2012 03:01:26 %S A181964 1,1,6,36,240,2160,20160,241920,2903040,39916800,578793600,9580032000, %T A181964 161902540800,3007651046400,58845346560000,1234444603392000, %U A181964 26854400821248000,624231436308480000,15083992450695168000,385614968295997440000 %N A181964 Sum of the sizes of normalizers of all the cyclic subgroups of Alternating Group of order n. %C A181964 For each cyclic subgroup of the Alternate group on n symbols, add the size of its normalizer (permutations leaving the subgroup invariant by conjugation). %C A181964 a(7) is remarquable because it is equal to the size of Alt(8). %F A181964 a(n) = n!/2 * A046682(n). %e A181964 Decomposing by number of cyclic subgroups * size of normalizer of subgroups %e A181964 a(5) = 1*60 + 4*15 + 6*10 + 0*60 + 10*6 = 240. %e A181964 a(6) = 1*360 + 8*45 + (18*20+18*20) + 8*45 + 10*36 = 2160. %Y A181964 Cf. A053529, A181950. %K A181964 nonn,easy %O A181964 1,3 %A A181964 _Olivier Gérard_, Apr 04 2012