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Number of symmetric n X n 01-matrices with maximum number of 1s and no 2 X 2 all-1 submatrix.
1

%I #8 Apr 08 2022 00:52:47

%S 1,1,2,4,16,170,360,840,82320,181440,1512000,19958400,79833600,

%T 259459200,14529715200

%N Number of symmetric n X n 01-matrices with maximum number of 1s and no 2 X 2 all-1 submatrix.

%F a(n) is the last element in the n-th row of triangle A350189.

%F Conjecture: the maximum number of 1s equals A072567(n), and so a(n) = A350189(n, A072567(n)).

%Y Cf. A072567, A191874, A191966, A335820, A350189, A351335, A352258.

%K nonn,more

%O 0,3

%A _Max Alekseyev_, Apr 03 2022