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A073584 Commuting even permutations: number of ordered pairs g, h in the alternating group A_n such that gh = hg. 2

%I

%S 1,1,9,48,300,2520,22680,282240,3265920,43545600,618710400,

%T 10298534400,171243072000,3138418483200,61460695296000,

%U 1286751578112000,27743619391488000,640237370572800000,15448927751921664000,394130125324615680000,10422552203028725760000,288306186674956369920000

%N Commuting even permutations: number of ordered pairs g, h in the alternating group A_n such that gh = hg.

%H N. J. A. Sloane, <a href="/A073584/b073584.txt">Table of n, a(n) for n = 1..37</a>

%F For n>=2 : a(n) = (n!/2) * A000702(n).

%Y Cf. A000702, A053529.

%K nonn

%O 1,3

%A Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 13 2003

%E More terms from _N. J. A. Sloane_ (based on A000720), Dec 31 2006

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Last modified May 26 17:16 EDT 2022. Contains 354092 sequences. (Running on oeis4.)