A269278 Number of 3 X n 0..3 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling three exactly once.

0, 1620, 46872, 1104264, 23549400, 474819408, 9230973192, 174918307032, 3252108138552, 59583135523968, 1078987217468328, 19354648265646120, 344454190256524824, 6089633274402902448, 107049250394211722184

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 36*a(n-1) - 378*a(n-2) + 972*a(n-3) - 729*a(n-4) for n>7.

Empirical g.f.: 36*x^2*(45 - 318*x + 812*x^2 - 1698*x^3 + 2061*x^4 - 756*x^5) / (1 - 18*x + 27*x^2)^2. - Colin Barker, Jan 21 2019

Example

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

Crossrefs

Row 3 of A269276.

Sequence in context: A345597 A345856 A206537 * A269184 A269150 A269212

Adjacent sequences: A269275 A269276 A269277 * A269279 A269280 A269281

Keyword

nonn

Author

R. H. Hardin, Feb 21 2016

Status

approved