A266049 Number of n X 2 integer arrays with each element equal to the number of horizontal and antidiagonal neighbors less than or equal to itself.

3, 7, 35, 176, 819, 3927, 18711, 89179, 425184, 2026855, 9662395, 46062279, 219586403, 1046805072, 4990293595, 23789558831, 113408780759, 540638504187, 2577313596096, 12286482224079, 58571702593459, 279221040017415

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 7*a(n-2) + 7*a(n-3) - a(n-4).

Empirical g.f.: x*(3 - 2*x - 7*x^2 + x^3) / (1 - 3*x - 7*x^2 - 7*x^3 + x^4). - Colin Barker, Jan 09 2019

Example

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

Crossrefs

Column 2 of A266055.

Sequence in context: A240272 A053530 A215575 * A132102 A081555 A301341

Adjacent sequences: A266046 A266047 A266048 * A266050 A266051 A266052

Keyword

nonn

Author

R. H. Hardin, Dec 20 2015

Status

approved