A128413 Inverse of number triangle A128412.

1, 2, 1, 12, 8, 1, 80, 60, 12, 1, 560, 448, 112, 16, 1, 4032, 3360, 960, 180, 20, 1, 29568, 25344, 7920, 1760, 264, 24, 1, 219648, 192192, 64064, 16016, 2912, 364, 28, 1, 1647360, 1464320, 512512, 139776, 29120, 4480, 480, 32, 1, 12446720

Offset

0,2

Comments

First column is A069723.

Links

Table of n, a(n) for n=0..45.

Formula

Number triangle T(n,k)=if(k=0,2^n*(C(2n,n)/2+0^n/2),2^(n-k)*C(2n,n-k)); Column k has g.f. if(k=0,4x/(sqrt(1-8x)(1-sqrt(1-8x))),(1/sqrt(1-8x))*((1-4x-sqrt(1-8x))/(8x))^k);

Example

Triangle begins
1,
2, 1,
12, 8, 1,
80, 60, 12, 1,
560, 448, 112, 16, 1,
4032, 3360, 960, 180, 20, 1,
29568, 25344, 7920, 1760, 264, 24, 1,
219648, 192192, 64064, 16016, 2912, 364, 28, 1

Crossrefs

Cf. A128417.

Sequence in context: A257635 A085752 A074966 * A058843 A343861 A130559

Adjacent sequences: A128410 A128411 A128412 * A128414 A128415 A128416

Keyword

easy,nonn,tabl

Author

Paul Barry, Mar 02 2007

Status

approved