A331646 Number of nonnegative integer matrices with 2 columns and any number of distinct nonzero rows with column sums n.

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

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 A363656 A300701

Adjacent sequences: A331643 A331644 A331645 * A331647 A331648 A331649

Keyword

nonn

Author

Andrew Howroyd, Jan 23 2020

Status

approved