A181201 - OEIS

A181201

a(n) = 0!*1!*2!*(3*n)!*3*n*(n-1) / ((n)!*(n+1)!*(n+2)!).

0, 30, 756, 16632, 360360, 7876440, 174594420, 3926434512, 89492111280, 2064420294300, 48134517631200, 1133012491934400, 26895067957892160, 643240375326254160, 15487976684184750900, 375182135475713517600

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OFFSET

1,2

COMMENTS

(Empirical) Number of n X 3 matrices containing a defective permutation of 1..3*n in strictly increasing order rowwise and columnwise, with one permutation value omitted and one repeated (see example).

Column 3 of A181204.

LINKS

R. H. Hardin, Table of n, a(n) for n=1..50

EXAMPLE

Some solutions for 4 X 3

..1..3..4....1..4..6....1..4..6....1..2..8....1..2..7....1..2..8....1..2..3

..2..6..9....2..5..7....2..7..9....3..4..9....2..5..9....2..5..9....2..6..7

..7..8.10....3..9.11....3..8.11....5..7.11....3..8.11....3..6.11....5..8..9

.10.11.12....5.10.12....7.10.12....6..9.12....6.10.12....7.10.12...10.11.12

CROSSREFS

Cf. A181204.

Sequence in context: A053509 A273435 A259345 * A089507 A045689 A096722

Adjacent sequences: A181198 A181199 A181200 * A181202 A181203 A181204

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 10 2010

STATUS

approved