A275498 - OEIS

A275498

Number of n X 2 0..2 arrays with no element equal to any value at offset (-2,-1) (-2,0) or (-1,-1) and new values introduced in order 0..2.

2, 9, 16, 28, 56, 104, 200, 380, 724, 1380, 2628, 5008, 9540, 18176, 34628, 65972, 125688, 239456, 456204, 869144, 1655864, 3154696, 6010220, 11450468, 21815044, 41561284, 79181152, 150853252, 287400512, 547545732, 1043165604, 1987403816

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OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = a(n-1) + 2*a(n-2) - a(n-4) for n>6.

Empirical g.f.: x*(2 + 7*x + 3*x^2 - 6*x^3 - 2*x^4 + x^5) / (1 - x - 2*x^2 + x^4). - Colin Barker, Feb 04 2019

EXAMPLE

Some solutions for n=4:

..0..1. .0..0. .0..0. .0..0. .0..1. .0..1. .0..1. .0..0. .0..0. .0..0

..1..1. .1..1. .1..1. .1..1. .1..1. .1..1. .1..1. .0..1. .0..1. .0..1

..2..2. .1..2. .1..2. .2..2. .2..2. .1..2. .1..2. .1..2. .1..2. .1..1

..0..0. .2..2. .2..0. .2..0. .2..0. .2..0. .0..0. .2..2. .1..2. .1..2

CROSSREFS

Column 2 of A275504.

Sequence in context: A003325 A338667 A101420 * A248434 A275395 A213389

Adjacent sequences: A275495 A275496 A275497 * A275499 A275500 A275501

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 30 2016

STATUS

approved