A107870 - OEIS

A107870

Triangle, read by rows, where T(n,k) = C(n*(n-1)/2-k*(k-1)/2+n-k+2, n-k).

1, 3, 1, 10, 4, 1, 56, 21, 5, 1, 495, 165, 36, 6, 1, 6188, 1820, 364, 55, 7, 1, 100947, 26334, 4845, 680, 78, 8, 1, 2035800, 475020, 80730, 10626, 1140, 105, 9, 1, 48903492, 10295472, 1623160, 201376, 20475, 1771, 136, 10, 1, 1362649145, 260932815

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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..46.

EXAMPLE

Triangle begins:

3,1;

10,4,1;

56,21,5,1;

495,165,36,6,1;

6188,1820,364,55,7,1;

100947,26334,4845,680,78,8,1;

2035800,475020,80730,10626,1140,105,9,1; ...

PROG

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

CROSSREFS

Cf. A107862, A107865, A107867, A107876, A107871, A107872.

Sequence in context: A126954 A176992 A319375 * A078817 A316193 A091042

Adjacent sequences: A107867 A107868 A107869 * A107871 A107872 A107873

KEYWORD

nonn,tabl

AUTHOR

Paul D. Hanna, Jun 04 2005

STATUS

approved