A233490 Number of (n+2) X (1+2) 0..2 arrays with no increasing sequence of length 3 horizontally or antidiagonally downwards.

16928, 424009, 10619963, 265993633, 6662227346, 166865923720, 4179418541288, 104680086586273, 2621876804023319, 65669013082159633, 1644783337099349594, 41196176081023328236, 1031822785055468622752, 25843618535508922362697

Offset

1,1

Links

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

Formula

Empirical: a(n) = 25*a(n-1) + 2*a(n-2) - 21*a(n-3) + 3*a(n-4).

Empirical g.f.: x*(16928 + 809*x - 14118*x^2 + 2028*x^3) / ((1 + x)*(1 - 26*x + 24*x^2 - 3*x^3)). - Colin Barker, Oct 11 2018

Example

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

Crossrefs

Column 1 of A233497.

Sequence in context: A035922 A233497 A233498 * A233489 A205606 A205437

Adjacent sequences: A233487 A233488 A233489 * A233491 A233492 A233493

Keyword

nonn

Author

R. H. Hardin, Dec 11 2013

Status

approved