A362650 - OEIS

%I #7 May 03 2023 10:51:52

%S 1,1,4,7,29,63,258,759,3263,12250,56330,250841,1235205,6113154,

%T 31941407,169613842,932670975,5223815423,30040926830,175918987173,

%U 1053086891249,6413469553076,39818396779256,251251607202822,1613056058498375,10514730684539068

%N Number of nonisomorphic unordered triples of involutions on an n-set.

%C Isomorphism is up to permutation of the elements of the n-set.

%H Andrew Howroyd, <a href="/A362650/b362650.txt">Table of n, a(n) for n = 0..50</a>

%e The a(3) = 7 nonisomorphic triples of involutions are:

%e   {(), (), ()},

%e   {(), (), (23)},

%e   {(), (23), (23)},

%e   {(), (23), (12)},

%e   {(23), (23), (23)},

%e   {(23), (23), (12)},

%e   {(23), (12), (13)}.

%Y Column k=3 of A362648.

%Y Cf. A362646, A362649.

%K nonn

%O 0,3

%A _Andrew Howroyd_, May 01 2023