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A215784 Number of permutations of 0..floor((n*6-1)/2) on even squares of an n X 6 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing. 1
1, 2, 12, 29, 189, 458, 2988, 7241, 47241, 114482, 746892, 1809989, 11808549, 28616378, 186696108, 452432081, 2951712081, 7153064162, 46667304972, 113091730349, 737821743309, 1788008493098, 11665145978028, 28268860698521 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 6 of A215788.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 16*a(n-2) - 3*a(n-4).

Empirical g.f.: x*(1 + 3*x)*(1 - x - x^2) / (1 - 16*x^2 + 3*x^4). - Colin Barker, Jul 23 2018

EXAMPLE

Some solutions for n=4:

..0..x..1..x..3..x....0..x..1..x..3..x....0..x..1..x..2..x....0..x..1..x..2..x

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

..4..x..6..x..9..x....4..x..6..x..9..x....5..x..7..x..9..x....6..x..7..x..9..x

..x..7..x.10..x.11....x..8..x.10..x.11....x..8..x.10..x.11....x..8..x.10..x.11

CROSSREFS

Cf. A215788.

Sequence in context: A326517 A248119 A240764 * A061780 A249411 A156021

Adjacent sequences:  A215781 A215782 A215783 * A215785 A215786 A215787

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 23 2012

STATUS

approved

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Last modified August 12 05:33 EDT 2020. Contains 336438 sequences. (Running on oeis4.)