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%I #12 Jan 26 2014 11:56:08
%S 1,1,3,42,914,23694,1048542,45379878,3272115926,257662344206,
%T 27726935045366,3101635433302996,474878584235678020,
%U 76786899439922296204,15844064187141655171020,3326909755872288926885670,897661138669999282018222470,246381314116108359863665821750
%N a(n) is the sum of the squares of the sizes of the conjugacy classes in the symmetric group A_n.
%C a(n) is the sum over all elements of Alt_n of the size of their conjugacy class. Each conjugacy class is thus counted as many times as its size, giving a sum of squares.
%e For n=5, a(5) = 1 + 12^2 + 12^2 + 15^2 + 20^2 = 914.
%e The class equation of A_5 is 1 + 12 + 12 + 15 + 20 = 60 = 5!/2
%o (GAP) A206820 := n -> Sum(ConjugacyClasses(AlternatingGroup(n)), c->Size(c)^2); # _Eric M. Schmidt_, Jan 26 2014
%Y A087132 (sequence for S_n), A000702 (conjugacy classes in A_n)
%K nonn,nice,easy
%O 1,3
%A _Olivier Gérard_, Feb 12 2012
%E More terms from _Eric M. Schmidt_, Jan 26 2014