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%I #15 Oct 14 2024 11:36:46
%S 1,3,9,87,5673,2577513,8459809773,207495141083975,
%T 39125696231091082665,57899300601363050181107733,
%U 683382115404724657577266518831159,65156055488094891194179319045960728827635,50704966066306827486637758645370695372532720829085
%N Number of n X n 0..2 matrices with all row and column sums equal.
%e Some solutions for n=4
%e ..1..1..0..1....0..0..2..1....2..0..1..1....2..0..2..2....2..1..1..0
%e ..0..2..1..0....1..1..1..0....0..1..2..1....1..2..1..2....0..2..0..2
%e ..2..0..0..1....2..0..0..1....2..1..0..1....1..2..2..1....1..0..2..1
%e ..0..0..2..1....0..2..0..1....0..2..1..1....2..2..1..1....1..1..1..1
%Y Column k=2 of A202784.
%K nonn
%O 0,2
%A _R. H. Hardin_, Feb 20 2002
%E a(7) and example from _R. H. Hardin_, Jan 05 2012
%E a(8)-a(12) from _Andrew Howroyd_, Jun 01 2017
%E a(0)=1 prepended by _Andrew Howroyd_, Oct 14 2024