A219136 Unchanging value maps: number of n X 2 binary arrays indicating the locations of corresponding elements unequal to no horizontal, diagonal or antidiagonal neighbor in a random 0..2 n X 2 array.
2, 6, 18, 51, 142, 405, 1157, 3289, 9344, 26580, 75621, 215076, 611683, 1739781, 4948421, 14074414, 40030688, 113856507, 323834334, 921058929, 2619701953, 7451032833, 21192445976, 60276171664, 171439240421, 487612482144
Offset: 1
Keywords
Examples
Some solutions for n=3: ..1..0....0..0....0..0....0..0....1..1....0..0....0..0....0..0....1..1....0..0 ..0..0....1..0....0..0....0..0....0..1....0..1....1..0....0..1....1..0....0..0 ..0..1....1..1....1..0....0..0....0..0....0..0....0..0....1..1....0..0....1..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A219142.
Formula
Empirical: a(n) = 2*a(n-1) + a(n-2) + 3*a(n-3) + 4*a(n-4) - 2*a(n-5) - 4*a(n-6).
Empirical g.f.: x*(2 + 2*x + 4*x^2 + 3*x^3 - 4*x^4 - 4*x^5) / ((1 + 2*x^2)*(1 - 2*x - 3*x^2 + x^3 + 2*x^4)). - Colin Barker, Mar 10 2018
Comments