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 A215785 Number of permutations of 0..floor((n*7-1)/2) on even squares of an n X 7 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing. 1

%I

%S 1,5,42,262,2465,15485,146205,918637,8674386,54503318,514658321,

%T 3233726365,30535100957,191859642509,1811672635826,11383190276278,

%U 107488026474001,675374034791837,6377352953765373,40070496565665517

%N Number of permutations of 0..floor((n*7-1)/2) on even squares of an n X 7 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.

%C Column 7 of A215788.

%H R. H. Hardin, <a href="/A215785/b215785.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 61*a(n-2) - 99*a(n-4) - 2*a(n-6).

%F Empirical g.f.: x*(1 + 5*x - 19*x^2 - 43*x^3 + 2*x^4 - 2*x^5) / (1 - 61*x^2 + 99*x^4 + 2*x^6). - _Colin Barker_, Jul 23 2018

%e Some solutions for n=4:

%e ..0..x..1..x..2..x..3....0..x..1..x..3..x..4....0..x..1..x..2..x..6

%e ..x..4..x..6..x..7..x....x..2..x..5..x..6..x....x..3..x..4..x..8..x

%e ..5..x..8..x..9..x.12....7..x..8..x..9..x.10....5..x..7..x.10..x.12

%e ..x.10..x.11..x.13..x....x.11..x.12..x.13..x....x..9..x.11..x.13..x

%Y Cf. A215788.

%K nonn

%O 1,2

%A _R. H. Hardin_, Aug 23 2012

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Last modified August 12 09:05 EDT 2020. Contains 336438 sequences. (Running on oeis4.)