A106246 Number triangle T(n,k)=C(n,k)C(2,n-k).

1, 2, 1, 1, 4, 1, 0, 3, 6, 1, 0, 0, 6, 8, 1, 0, 0, 0, 10, 10, 1, 0, 0, 0, 0, 15, 12, 1, 0, 0, 0, 0, 0, 21, 14, 1, 0, 0, 0, 0, 0, 0, 28, 16, 1, 0, 0, 0, 0, 0, 0, 0, 36, 18, 1, 0, 0, 0, 0, 0, 0, 0, 0, 45, 20, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 55, 22, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 66, 24, 1, 0, 0, 0, 0, 0, 0

Offset

0,2

Comments

Row sums are C(n+2,2)=A000217(n+1). Diagonal sums are A106247. Subdiagonal is 2(n+1)=A005843(n+1). Second subdiagonal is A000217(n+1).

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Formula

T(n,k)=A007318*A167194. [From Mats Granvik, Oct 30 2009]

Example

Triangle begins
1;
2,1;
1,4,1;
0,3,6,1;
0,0,6,8,1;
0,0,0,10,10,1;

Mathematica

Flatten[Table[Binomial[n, k]Binomial[2, n-k], {n, 0, 20}, {k, 0, n}]] (* Harvey P. Dale, Jan 28 2016 *)

Crossrefs

Cf. A007318, A167194. [From Mats Granvik, Oct 30 2009]

Sequence in context: A087605 A251636 A248939 * A340660 A136674 A144383

Adjacent sequences: A106243 A106244 A106245 * A106247 A106248 A106249

Keyword

easy,nonn,tabl

Author

Paul Barry, Apr 26 2005

Status

approved