A208866 - OEIS

A208866

Number of n X 2 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.

2, 12, 143, 1979, 28246, 405481, 5826959, 83752328, 1203835147, 17303737555, 248721498050, 3575088704597, 51387836750983, 738641752044964, 10617135747615911, 152609260439813291, 2193584684852893774

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OFFSET

1,1

COMMENTS

Column 2 of A208872.

LINKS

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

FORMULA

Empirical: a(n) = 18*a(n-1) - 55*a(n-2) + 42*a(n-3) - 9*a(n-4) for n>5.

Empirical g.f.: x*(2 - 24*x + 37*x^2 - 19*x^3 + 3*x^4) / ((1 - 3*x + x^2)*(1 - 15*x + 9*x^2)). - Colin Barker, Jul 07 2018

EXAMPLE

Some solutions for n=4: