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A215869 Number of permutations of 0..floor((n*9-2)/2) on odd squares of an nX9 array such that each row, column, diagonal and (downwards) antidiagonal of odd squares is increasing.

%I A215869 #6 Jul 22 2025 23:25:51
%S A215869 1,14,290,11694,307874,14296434,386699176,18255280444,494952307400,
%T A215869 23397688110992,634501639410480,29997930933948284,813501010455768664,
%U A215869 38461009542931961924,1043008988814913191696,49311812528326463481148
%N A215869 Number of permutations of 0..floor((n*9-2)/2) on odd squares of an nX9 array such that each row, column, diagonal and (downwards) antidiagonal of odd squares is increasing.
%C A215869 Column 9 of A215870
%H A215869 R. H. Hardin, <a href="/A215869/b215869.txt">Table of n, a(n) for n = 1..210</a>
%F A215869 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 A215869 Some solutions for n=4
%e A215869 ..x..0..x..2..x..4..x..8..x....x..0..x..2..x..4..x..6..x
%e A215869 ..1..x..3..x..5..x.11..x.12....1..x..3..x..7..x.10..x.13
%e A215869 ..x..6..x..7..x.13..x.14..x....x..5..x..9..x.12..x.15..x
%e A215869 ..9..x.10..x.15..x.16..x.17....8..x.11..x.14..x.16..x.17
%K A215869 nonn
%O A215869 1,2
%A A215869 _R. H. Hardin_ Aug 25 2012