A167194 Triangle read by rows. A130713 in the columns.

1, 2, 1, 1, 2, 1, 0, 1, 2, 1, 0, 0, 1, 2, 1, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 1

Offset

1,2

Links

Table of n, a(n) for n=1..91.

Formula

From Peter Bala, Sep 12 2012: (Start)

T(n,k) = binomial(2,n-k).

O.g.f.: (1+x)^2/(1-t*x).

Riordan array ((1+x)^2,x).

Matrix inverse is signed version of A004736. (End)

Example

Table begins:
  1;
  2,1;
  1,2,1;
  0,1,2,1;
  0,0,1,2,1;
  0,0,0,1,2,1;
  0,0,0,0,1,2,1;
  0,0,0,0,0,1,2,1;
  0,0,0,0,0,0,1,2,1;
  0,0,0,0,0,0,0,1,2,1;
  0,0,0,0,0,0,0,0,1,2,1;
  ...

Mathematica

Array[PadLeft[{1, 2, 1}, #] &, 15] (* Paolo Xausa, Jun 27 2024 *)

Crossrefs

Cf. A004736, A130713, A185018.

Sequence in context: A014570 A015131 A282716 * A185018 A333289 A099075

Adjacent sequences: A167191 A167192 A167193 * A167195 A167196 A167197

Keyword

nonn,tabl

Author

Mats Granvik, Oct 30 2009

Status

approved