A122919 Inverse of Riordan array (1/(1+x+x^2),x/(1+x)^2).

1, 1, 1, 3, 3, 1, 9, 10, 5, 1, 28, 34, 21, 7, 1, 90, 117, 83, 36, 9, 1, 297, 407, 319, 164, 55, 11, 1, 1001, 1430, 1209, 702, 285, 78, 13, 1, 3432, 5070, 4550, 2898, 1350, 454, 105, 15, 1, 11934, 18122, 17068, 11696, 6052

Offset

0,4

Comments

Row sums are A097613. Diagonal sums are A122920. Inverse of A122917.

Links

Table of n, a(n) for n=0..49.

Formula

Riordan array ((1-3x+2x^2-(1-x)sqrt(1-4x))/(2x^2),(1-2x-sqrt(1-4x))/(2x))

Example

Triangle begins
1,
1, 1,
3, 3, 1,
9, 10, 5, 1,
28, 34, 21, 7, 1,
90, 117, 83, 36, 9, 1,
297, 407, 319, 164, 55, 11, 1,
1001, 1430, 1209, 702, 285, 78, 13, 1

Crossrefs

Sequence in context: A108075 A215120 A084145 * A188513 A260301 A216916

Adjacent sequences: A122916 A122917 A122918 * A122920 A122921 A122922

Keyword

easy,nonn,tabl

Author

Paul Barry, Sep 19 2006

Status

approved