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A215787 Number of permutations of 0..floor((n*9-1)/2) on even squares of an nX9 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.

%I A215787 #6 Jul 22 2025 23:24:32
%S A215787 1,14,462,11694,530429,14296434,673507749,18255280444,862827082115,
%T A215787 23397688110992,1106178923600669,29997930933948284,
%U A215787 1418251919293188195,38461009542931961924,1818375422885354065137,49311812528326463481148
%N A215787 Number of permutations of 0..floor((n*9-1)/2) on even squares of an nX9 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.
%C A215787 Column 9 of A215788
%H A215787 R. H. Hardin, <a href="/A215787/b215787.txt">Table of n, a(n) for n = 1..210</a>
%F A215787 Empirical: a(n) = 1385*a(n-2) -131648*a(n-4) -318070*a(n-6) -4160916*a(n-8) -1097892*a(n-10) +648*a(n-12)
%e A215787 Some solutions for n=4
%e A215787 ..0..x..1..x..3..x..6..x..8....0..x..1..x..2..x..6..x.11
%e A215787 ..x..2..x..5..x.10..x.13..x....x..3..x..5..x..8..x.12..x
%e A215787 ..4..x..7..x.11..x.14..x.15....4..x..7..x.10..x.14..x.16
%e A215787 ..x..9..x.12..x.16..x.17..x....x..9..x.13..x.15..x.17..x
%K A215787 nonn
%O A215787 1,2
%A A215787 _R. H. Hardin_ Aug 23 2012