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A215789 Number of permutations of 0..floor((3*n-1)/2) on even squares of an 3*n array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing 0
1, 1, 1, 2, 5, 12, 42, 110, 462, 1274, 6006, 17136, 87516, 255816, 1385670, 4124406, 23371634, 70549050, 414315330, 1264752060, 7646001090, 23555382240, 145862174640, 452806924752, 2861142656400, 8939481277552, 57468093927120 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Row 3 of A215788

LINKS

Table of n, a(n) for n=1..27.

EXAMPLE

Some solutions for n=5

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

..x..3..x..5..x....x..2..x..5..x....x..2..x..4..x....x..3..x..4..x

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

CROSSREFS

Sequence in context: A005664 A009739 A062272 * A127137 A172239 A183758

Adjacent sequences:  A215786 A215787 A215788 * A215790 A215791 A215792

KEYWORD

nonn

AUTHOR

R. H. Hardin Aug 23 2012

STATUS

approved

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Last modified December 8 16:05 EST 2021. Contains 349596 sequences. (Running on oeis4.)