A252869 Number of n X n nonnegative integer arrays with upper left 0 and lower right 2n-4 and value increasing by 0 or 1 with every step right or down.

0, 1, 44, 615, 7313, 85801, 1030330, 12742873, 161937617, 2105918045, 27918122131, 376111502977, 5136280530303, 70961632168027, 990271171218092, 13940676224604419, 197768060575469207, 2824828302263709187, 40595088350375470407, 586585037283553891311

Offset

1,3

Links

Table of n, a(n) for n=1..20.

Example

Some solutions for n=3
..0..0..1....0..0..0....0..0..1....0..1..1....0..1..1....0..1..2....0..1..2
..1..1..1....0..0..1....0..0..1....1..1..2....0..1..1....0..1..2....1..2..2
..1..2..2....1..1..2....0..1..2....1..2..2....1..2..2....1..1..2....2..2..2

Crossrefs

Main diagonal of A252876.

Column d=2 of A323849.

Sequence in context: A264680 A356415 A289647 * A296649 A221505 A160066

Adjacent sequences: A252866 A252867 A252868 * A252870 A252871 A252872

Keyword

nonn

Author

R. H. Hardin, Dec 24 2014

Extensions

a(16)-a(20) from Alois P. Heinz, Feb 07 2019

Status

approved