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 A331646 Number of nonnegative integer matrices with 2 columns and any number of distinct nonzero rows with column sums n. 5
 1, 3, 13, 87, 539, 2483, 14567, 81669, 402187, 2089413, 10344053, 49065413, 232941293, 1092284091, 5011510213, 22637050383, 100092546203, 439274499155, 1888145728847, 8058486875493, 33954688300771, 140741748208701, 579404121062837, 2354567807958773, 9481400353625789 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 0..100 EXAMPLE The a(1) = 3 matrices are:   [1 0]  [0 1]  [1 1]   [0 1]  [1 0] PROG (PARI) a(n)={subst(serlaplace(polcoef(polcoef(prod(i=0, n, prod(j=0, n, 1 + x^i*y^j*z + O(x*x^n) + O(y*y^n))), n, x), n, y)/(1 + z)), z, 1)} CROSSREFS Column k=2 of A331568. Cf. A331647, A331706, A331711. Sequence in context: A188204 A152112 A167810 * A054420 A300701 A174278 Adjacent sequences:  A331643 A331644 A331645 * A331647 A331648 A331649 KEYWORD nonn AUTHOR Andrew Howroyd, Jan 23 2020 STATUS approved

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Last modified December 9 06:07 EST 2021. Contains 349627 sequences. (Running on oeis4.)