A122431 Riordan array ((1+x)^3,x).

1, 3, 1, 3, 3, 1, 1, 3, 3, 1, 0, 1, 3, 3, 1, 0, 0, 1, 3, 3, 1, 0, 0, 0, 1, 3, 3, 1, 0, 0, 0, 0, 1, 3, 3, 1, 0, 0, 0, 0, 0, 1, 3, 3, 1, 0, 0, 0, 0, 0, 0, 1, 3, 3, 1, 0, 0, 0, 0, 0, 0, 0, 1

Offset

0,2

Comments

Row sums are A115291. Diagonal sums are A113311. Inverse is A122432. Sequence array for C(3,n).

Links

Table of n, a(n) for n=0..62.

Formula

Number triangle T(n,k)=C(3,n-k)

Example

Triangle begins
1,
3,1,
3,3,1,
1,3,3,1,
0,1,3,3,1,
0,0,1,3,3,1,
0,0,0,1,3,3,1,
0,0,0,0,1,3,3,1

Crossrefs

Sequence in context: A359525 A124814 A122567 * A279340 A089607 A216637

Adjacent sequences: A122428 A122429 A122430 * A122432 A122433 A122434

Keyword

easy,nonn,tabl

Author

Paul Barry, Sep 04 2006

Status

approved