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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.)