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A107867 Triangle, read by rows, where T(n,k) = C(n*(n-1)/2-k*(k-1)/2+n-k+1,n-k). 12
1, 2, 1, 6, 3, 1, 35, 15, 4, 1, 330, 120, 28, 5, 1, 4368, 1365, 286, 45, 6, 1, 74613, 20349, 3876, 560, 66, 7, 1, 1560780, 376740, 65780, 8855, 969, 91, 8, 1, 38608020, 8347680, 1344904, 169911, 17550, 1540, 120, 9, 1, 1101716330, 215553195, 32224114 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Remarkably, the following matrix products are all equal to A107876: A107862^-1*A107867 = A107867^-1*A107870 = A107870^-1*A107873.

LINKS

Table of n, a(n) for n=0..47.

EXAMPLE

Triangle begins:

1;

2,1;

6,3,1;

35,15,4,1;

330,120,28,5,1;

4368,1365,286,45,6,1;

74613,20349,3876,560,66,7,1;

1560780,376740,65780,8855,969,91,8,1; ...

PROG

(PARI) T(n, k)=binomial(n*(n-1)/2-k*(k-1)/2 +n-k+1, n-k)

CROSSREFS

Cf. A107862, A107864, A107865, A107867, A107870, A107876.

Sequence in context: A222159 A221623 A096334 * A158442 A252095 A120435

Adjacent sequences:  A107864 A107865 A107866 * A107868 A107869 A107870

KEYWORD

nonn,tabl

AUTHOR

Paul D. Hanna, Jun 04 2005

STATUS

approved

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Last modified December 5 17:42 EST 2019. Contains 329768 sequences. (Running on oeis4.)