|
%I #4 Apr 08 2020 21:16:36
%S 1,1,2,5,12,29,79,225,677,2141,7121,24693,89117,333312,1288949,
%T 5140039,21094565,88931387,384544989,1703083332,7715920544,
%U 35720666818,168809971994,813633173238,3996247863791,19986651995983,101715962631912,526405121697307,2768690275913665,14791474244527076,80224577967948446
%N Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 3 up to permutations of rows and columns.
%e The a(2) = 2 matrices are:
%e [0 3] [1 2]
%e [3 0] [2 1]
%Y Column k=3 of A333737.
%K nonn
%O 0,3
%A _Andrew Howroyd_, Apr 08 2020
|
