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A119828 Number triangle T(n,k)=(2n)!/(2k)!. 3
1, 2, 1, 24, 12, 1, 720, 360, 30, 1, 40320, 20160, 1680, 56, 1, 3628800, 1814400, 151200, 5040, 90, 1, 479001600, 239500800, 19958400, 665280, 11880, 132, 1, 87178291200, 43589145600, 3632428800, 121080960, 2162160, 24024, 182, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Row sums are A051396(n+1). Diagonal sums are A119829. Inverse is the bi-diagonal array A119830. E.g.f. cosh(x*y)/(1-y*x^2) produces an aerated version.

LINKS

Table of n, a(n) for n=0..35.

FORMULA

Number triangle T(n,k)=[k<=n](2n)!/(2k)!

EXAMPLE

Triangle begins

1,

2, 1,

24, 12, 1,

720, 360, 30, 1,

40320, 20160, 1680, 56, 1,

3628800, 1814400, 151200, 5040, 90, 1

CROSSREFS

Sequence in context: A037943 A073876 A276399 * A297892 A101179 A184295

Adjacent sequences:  A119825 A119826 A119827 * A119829 A119830 A119831

KEYWORD

easy,nonn,tabl

AUTHOR

Paul Barry, May 25 2006

STATUS

approved

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Last modified October 16 20:35 EDT 2019. Contains 328103 sequences. (Running on oeis4.)