A268624 Number of n X 4 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once.

60, 666, 6300, 55452, 467190, 3819654, 30553014, 240364746, 1866503592, 14342680944, 109265781870, 826421076378, 6212333663082, 46453421706210, 345772280726172, 2563402622459652, 18936504080614278, 139446644995253358

Offset

1,1

Links

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

Formula

Empirical: a(n) = 18*a(n-1) - 111*a(n-2) + 282*a(n-3) - 333*a(n-4) + 180*a(n-5) - 36*a(n-6) for n>7.

Empirical g.f.: 6*x*(10 - 69*x + 162*x^2 - 157*x^3 + 87*x^4 - 36*x^5 + 8*x^6) / (1 - 9*x + 15*x^2 - 6*x^3)^2.- Colin Barker, Jan 14 2019

Example

Some solutions for n=4:
..1..2..2..2. .2..0..1..2. .2..2..2..2. .0..0..1..2. .2..1..0..1
..0..1..2..1. .2..1..2..2. .1..2..2..2. .0..1..2..2. .2..2..1..0
..1..2..1..0. .1..2..1..2. .2..2..2..2. .1..2..2..2. .2..1..0..1
..0..1..0..1. .2..1..0..1. .1..1..2..1. .0..2..2..2. .1..2..1..2

Crossrefs

Column 4 of A268628.

Sequence in context: A324068 A223242 A244837 * A088945 A269189 A136008

Adjacent sequences: A268621 A268622 A268623 * A268625 A268626 A268627

Keyword

nonn

Author

R. H. Hardin, Feb 09 2016

Status

approved