A274854 Number of n X 4 0..2 arrays with no element equal to any value at offset (-1,0) (0,-1) or (-2,-2) and new values introduced in order 0..2.

4, 27, 43, 118, 330, 923, 2585, 7253, 20368, 57205, 160656, 451182, 1267101, 3558565, 9994005, 28067514, 78825751, 221376890, 621722366, 1746066251, 4903711869, 13771751157, 38677054168, 108621953977, 305057588980, 856734105714

Offset

1,1

Links

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

Formula

Empirical: a(n) = 5*a(n-1) - 9*a(n-2) + 10*a(n-3) - 6*a(n-4) + a(n-5) for n>7.

Empirical g.f.: x*(4 + 7*x - 56*x^2 + 106*x^3 - 119*x^4 + 63*x^5 - 9*x^6) / ((1 - x)*(1 - 4*x + 5*x^2 - 5*x^3 + x^4)). - Colin Barker, Jan 31 2019

Example

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

Crossrefs

Column 4 of A274858.

Sequence in context: A239283 A082872 A372487 * A054411 A051506 A370492

Adjacent sequences: A274851 A274852 A274853 * A274855 A274856 A274857

Keyword

nonn

Author

R. H. Hardin, Jul 09 2016

Status

approved