A263366 Number of (n+1) X (1+1) 0..2 arrays with each row and column divisible by 7, read as a base-3 number with top and left being the most significant digits.

1, 1, 2, 5, 10, 19, 37, 73, 146, 293, 586, 1171, 2341, 4681, 9362, 18725, 37450, 74899, 149797, 299593, 599186, 1198373, 2396746, 4793491, 9586981, 19173961, 38347922, 76695845, 153391690, 306783379, 613566757, 1227133513, 2454267026, 4908534053

Offset

1,3

Links

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

Formula

Empirical: a(n) = 3*a(n-1) - 3*a(n-2) + 3*a(n-3) - 3*a(n-4) + 3*a(n-5) - 2*a(n-6).

Empirical g.f.: x*(1 - 2*x + 2*x^2 - x^3 + x^4 - 2*x^5) / ((1 - x)*(1 - 2*x)*(1 - x + x^2)*(1 + x + x^2)). - Colin Barker, Jan 01 2019

Example

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

Crossrefs

Column 1 of A263373.

Sequence in context: A061705 A052944 A132736 * A068035 A304973 A016029

Adjacent sequences: A263363 A263364 A263365 * A263367 A263368 A263369

Keyword

nonn

Author

R. H. Hardin, Oct 16 2015

Status

approved