A270113 Number of n X 3 0..7 arrays with some element plus some horizontally or vertically adjacent neighbor totaling seven exactly once.

112, 100800, 45440640, 16972694928, 5795977666752, 1877723928063648, 587581295287557312, 179399371883007424176, 53777749891851319065984, 15893068951375608455132544, 4643931350900992326932238336

Offset

1,1

Links

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

Formula

Empirical: a(n) = 540*a(n-1) - 75994*a(n-2) + 835380*a(n-3) - 2393209*a(n-4) for n>5.

Empirical g.f.: 112*x*(1 + 360*x - 4286*x^2 + 12339*x^3 + 1225*x^4) / (1 - 270*x + 1547*x^2)^2. - Colin Barker, Jan 29 2019

Example

Some solutions for n=2:
  3 3 4   0 7 5   4 2 0   2 2 3   3 6 3   2 1 5   4 2 5
  3 6 0   1 3 5   6 1 2   4 3 1   4 0 6   0 0 2   6 4 0

Crossrefs

Column 3 of A270118.

Sequence in context: A210292 A270146 A184898 * A275052 A180039 A261949

Adjacent sequences: A270110 A270111 A270112 * A270114 A270115 A270116

Keyword

nonn

Author

R. H. Hardin, Mar 11 2016

Status

approved