A181207 Number of n X 3 binary matrices with no two 1's adjacent diagonally or antidiagonally.

8, 25, 119, 484, 2117, 9025, 38936, 167281, 720083, 3097600, 13329209, 57350329, 246768392, 1061782225, 4568619071, 19657722436, 84582794333, 363940725625, 1565955363224, 6737954403049, 28991906279867, 124745667481600

Offset: 1

Author

R. H. Hardin, Oct 10 2010

Keywords

• nonn

Comments

Column 3 of A181212.

Links

• R. H. Hardin, Table of n, a(n) for n=1..400

Crossrefs

Cf. A181212.

Formula

Empirical: a(n) = 5*a(n-1) - 15*a(n-3) + 9*a(n-4).

Empirical g.f.: x*(8 - 15*x - 6*x^2 + 9*x^3) / ((1 - 5*x + 3*x^2)*(1 - 3*x^2)). - Colin Barker, Mar 26 2018