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.

1, 1, 11, 114, 2438, 73120, 3107640, 175157568, 12683256458, 1146644890542, 126603925984322, 16764298017398342, 2622239904802101734, 478350006311298468126, 100655530463934465864626, 24200010145455307873369888, 6592700960401481917596215614, 2020180735699844322843722782402

Offset: 1

Author

Andrew Howroyd, Feb 22 2020

Keywords

• nonn

Examples

			The a(2) = 1 matrix is:
   [1 1]
   [1 1]
		

Links

• Jean-François Alcover, Table of n, a(n) for n = 1..40 (all terms from Andrew Howroyd)

Crossrefs

Central coefficients of A269742.

Programs

Mathematica

A269742 = Cases[Import["https://oeis.org/A269742/b269742.txt", "Table"], {, }][[All, 2]];
a[n_] := A269742[[n^2 - n + 1]];
Array[a, 40] (* Jean-François Alcover, Feb 24 2020 *)