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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.
2
1, 1, 11, 114, 2438, 73120, 3107640, 175157568, 12683256458, 1146644890542, 126603925984322, 16764298017398342, 2622239904802101734, 478350006311298468126, 100655530463934465864626, 24200010145455307873369888, 6592700960401481917596215614, 2020180735699844322843722782402
OFFSET
1,3
LINKS
Jean-François Alcover, Table of n, a(n) for n = 1..40 (all terms from Andrew Howroyd)
EXAMPLE
The a(2) = 1 matrix is:
[1 1]
[1 1]
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 *)
CROSSREFS
Central coefficients of A269742.
Sequence in context: A201966 A121196 A251261 * A160465 A125446 A287838
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Feb 22 2020
STATUS
approved