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Number of idempotent non-symmetric n X n (0,1)-matrices over the reals.
0

%I #16 Aug 17 2020 13:34:53

%S 0,0,4,42,436,5650,96544,2185610,65108236

%N Number of idempotent non-symmetric n X n (0,1)-matrices over the reals.

%C Off diagonal entries of an idempotent symmetric n X n (0,1)-matrix must be zero.

%F a(n) = A086922(n) - A000079(n).

%e a(2) = 4 because [1,1] [0,1] [0,0] [1,0]

%e [0,0], [0,1], [1,1], [1,0], are non-symmetric and idemponent.

%Y Cf. A000079, A086922.

%K nonn,more

%O 0,3

%A _Torlach Rush_, Jun 22 2020