A203928 Number of (n+1) X 3 0..5 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements.

4356, 106596, 2543436, 60873876, 1456391916, 34845401556, 833700866796, 19946896311636, 477243883220076, 11418404289436116, 273193561903563756, 6536353100235366996, 156386964438192169836, 3741670970218511256276

Offset

1,1

Comments

Column 2 of A203934.

Links

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

Formula

Empirical: a(n) = 21*a(n-1) + 70*a(n-2).

Empirical g.f.: 36*x*(121 + 420*x) / (1 - 21*x - 70*x^2). - Colin Barker, Jun 05 2018

Example

Some solutions for n=4:
..3..3..5....5..4..0....1..4..4....3..0..5....5..3..5....2..0..5....1..1..5
..0..3..3....2..5..4....1..1..4....4..3..0....5..5..1....5..2..0....4..1..1
..4..0..3....5..4..1....1..5..1....2..4..3....5..1..5....0..5..2....1..4..1
..4..4..0....0..5..4....0..1..3....3..2..4....1..5..4....5..3..5....0..1..2
..3..4..4....3..0..5....2..0..1....5..3..2....3..1..5....5..5..5....5..0..1

Crossrefs

Cf. A203934.

Sequence in context: A250817 A154084 A285040 * A340457 A176111 A164517

Adjacent sequences: A203925 A203926 A203927 * A203929 A203930 A203931

Keyword

nonn

Author

R. H. Hardin, Jan 08 2012

Status

approved