A203916 Number of (n+2) X 3 0..1 arrays with every 3 X 3 subblock having equal diagonal elements or equal antidiagonal elements, and new values 0..1 introduced in row major order.

112, 392, 1400, 5000, 17800, 63368, 225704, 803912, 2863144, 10197128, 36317672, 129347528, 460677928, 1640728328, 5843540840, 20812080200, 74123322280, 263994125192, 940229020136, 3348675314888, 11926483984936, 42476802576392

Offset

1,1

Comments

Column 1 of A203923.

Links

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

Formula

Empirical: a(n) = 3*a(n-1) +6*a(n-3) +4*a(n-4).

Empirical g.f.: 8*x*(14 + 7*x + 28*x^2 + 16*x^3) / ((1 + 2*x^2)*(1 - 3*x - 2*x^2)). - Colin Barker, Jun 05 2018

Example

Some solutions for n=3:
..0..0..0....0..1..1....0..0..1....0..0..0....0..1..0....0..1..0....0..0..1
..1..0..0....1..0..1....1..0..1....1..0..0....0..0..0....0..0..0....1..1..1
..0..1..1....0..1..0....0..1..0....1..1..0....0..0..0....1..0..0....1..1..1
..1..1..1....1..0..0....1..0..1....0..1..1....0..0..1....0..1..0....1..1..1
..1..1..1....0..0..1....1..0..0....1..0..1....0..0..0....0..0..1....1..1..1

Crossrefs

Cf. A203923.

Sequence in context: A235319 A203923 A235312 * A234681 A234674 A217992

Adjacent sequences: A203913 A203914 A203915 * A203917 A203918 A203919

Keyword

nonn

Author

R. H. Hardin, Jan 07 2012

Status

approved