A119831 - OEIS

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A119831

Number triangle (3n)!/(3k)!.

1, 6, 1, 720, 120, 1, 362880, 60480, 504, 1, 479001600, 79833600, 665280, 1320, 1, 1307674368000, 217945728000, 1816214400, 3603600, 2730, 1, 6402373705728000, 1067062284288000, 8892185702400, 17643225600, 13366080, 4896, 1

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

0,2

COMMENTS

Row sums are A087350. Inverse is bi-diagonal array A119832.

LINKS

Table of n, a(n) for n=0..27.

FORMULA

Number triangle T(n,k)=[k<=n]*(3n)!/(3k)!

EXAMPLE

Triangle begins

6, 1,

720, 120, 1,

362880, 60480, 504, 1,

479001600, 79833600, 665280, 1320, 1,

1307674368000, 217945728000, 1816214400, 3603600, 2730, 1

MATHEMATICA

Flatten[Table[(3n)!/(3k)!, {n, 0, 10}, {k, 0, n}]] (* Harvey P. Dale, Jan 19 2013 *)

CROSSREFS

Cf. A119828.

Sequence in context: A183284 A224476 A123147 * A369016 A224842 A318138

Adjacent sequences: A119828 A119829 A119830 * A119832 A119833 A119834

KEYWORD

easy,nonn,tabl

AUTHOR

Paul Barry, May 25 2006

STATUS

approved