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A332729 Number of nonnegative integer n X n matrices with row and column sums 2 and sum of entries below the main diagonal n - 1.

%I A332729 #24 Feb 28 2020 02:02:33
%S A332729 1,1,11,114,2438,73120,3107640,175157568,12683256458,1146644890542,
%T A332729 126603925984322,16764298017398342,2622239904802101734,
%U A332729 478350006311298468126,100655530463934465864626,24200010145455307873369888,6592700960401481917596215614,2020180735699844322843722782402
%N A332729 Number of nonnegative integer n X n matrices with row and column sums 2 and sum of entries below the main diagonal n - 1.
%H A332729 Jean-François Alcover, <a href="/A332729/b332729.txt">Table of n, a(n) for n = 1..40</a> (all terms from Andrew Howroyd)
%e A332729 The a(2) = 1 matrix is:
%e A332729    [1 1]
%e A332729    [1 1]
%t A332729 A269742 = Cases[Import["https://oeis.org/A269742/b269742.txt", "Table"], {_, _}][[All, 2]];
%t A332729 a[n_] := A269742[[n^2 - n + 1]];
%t A332729 Array[a, 40] (* _Jean-François Alcover_, Feb 24 2020 *)
%Y A332729 Central coefficients of A269742.
%K A332729 nonn
%O A332729 1,3
%A A332729 _Andrew Howroyd_, Feb 22 2020