A228750 Number of n X 4 binary arrays with top left element equal to 1 and no two ones adjacent horizontally or antidiagonally.

3, 20, 126, 780, 4808, 29608, 182288, 1122240, 6908896, 42533440, 261849728, 1612032128, 9924194048, 61096565760, 376130326016, 2315580595200, 14255467112448, 87761291061248, 540287045521408, 3326182739886080

Offset

1,1

Links

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

Formula

Empirical: a(n) = 8*a(n-1) - 12*a(n-2) + 4*a(n-3).

Empirical g.f.: x*(3 - 4*x + 2*x^2) / (1 - 8*x + 12*x^2 - 4*x^3). - Colin Barker, Sep 12 2018

Example

Some solutions for n=4:
..1..0..1..0....1..0..0..0....1..0..0..0....1..0..0..0....1..0..1..0
..0..0..1..0....1..0..1..0....0..1..0..1....0..1..0..0....0..0..1..0
..1..0..0..1....1..0..0..1....0..1..0..1....0..0..1..0....1..0..1..0
..0..0..0..0....0..1..0..1....0..1..0..1....1..0..0..1....0..0..1..0

Crossrefs

Column 4 of A228754.

Sequence in context: A037795 A325890 A323563 * A187442 A167590 A228884

Adjacent sequences: A228747 A228748 A228749 * A228751 A228752 A228753

Keyword

nonn

Author

R. H. Hardin, Sep 02 2013

Status

approved