A215867 Number of permutations of 0..floor((n*7-2)/2) on odd squares of an n X 7 array such that each row, column, diagonal and (downwards) antidiagonal of odd squares is increasing.
1, 5, 29, 262, 1642, 15485, 97289, 918637, 5772013, 54503318, 342457898, 3233726365, 20318307913, 191859642509, 1205501906765, 11383190276278, 71523418913482, 675374034791837, 4243543228336841, 40070496565665517
Offset: 1
Keywords
Examples
Some solutions for n=4: ..x..0..x..2..x..4..x....x..0..x..2..x..4..x....x..0..x..2..x..4..x ..1..x..3..x..5..x..7....1..x..3..x..5..x..8....1..x..3..x..6..x..8 ..x..6..x..9..x.10..x....x..6..x..9..x.10..x....x..5..x..7..x.10..x ..8..x.11..x.12..x.13....7..x.11..x.12..x.13....9..x.11..x.12..x.13
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = 61*a(n-2) -99*a(n-4) -2*a(n-6).
Empirical: g.f.: -x*(-1 -5*x +32*x^2 +43*x^3 +28*x^4 +2*x^5) / ( 1 -61*x^2 +99*x^4 +2*x^6 ). - R. J. Mathar, Nov 27 2015
Comments