A239650 Number of 2 X n 0..3 arrays with no element equal to zero plus the sum of elements to its left or two plus the sum of the elements above it, modulo 4.

4, 20, 92, 418, 1898, 8588, 38888, 175974, 796550, 3604984, 16316908, 73849786, 334252546, 1512838756, 6847231728, 30990953678, 140267248638, 634858320528, 2873411390324, 13005245181090, 58862597882746, 266415951317884

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 12*a(n-2) - 18*a(n-3) - 29*a(n-4) + 19*a(n-5) + 38*a(n-6) + 8*a(n-7).

Empirical g.f.: 2*x*(2 + 4*x - 8*x^2 - 13*x^3 + 8*x^4 + 19*x^5 + 4*x^6) / (1 - 3*x - 12*x^2 + 18*x^3 + 29*x^4 - 19*x^5 - 38*x^6 - 8*x^7). - Colin Barker, Oct 26 2018

Example

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

Crossrefs

Row 2 of A239649.

Sequence in context: A070733 A166175 A094971 * A218837 A254943 A099025

Adjacent sequences: A239647 A239648 A239649 * A239651 A239652 A239653

Keyword

nonn

Author

R. H. Hardin, Mar 23 2014

Status

approved