cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A113680 Riordan array ((1-x-2x^2)/(1-x),x).

Original entry on oeis.org

1, 0, 1, -2, 0, 1, -2, -2, 0, 1, -2, -2, -2, 0, 1, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2
Offset: 0

Views

Author

Paul Barry, Nov 04 2005

Keywords

Comments

Inverse of A113678. Sequence array of A113679. Row sums are 3-2n-2*0^n. Diagonal sums are 1-n.

Examples

			Triangle begins
1;
0, 1;
-2, 0, 1;
-2, -2, 0, 1;
-2, -2, -2, 0, 1;
-2, -2, -2, -2, 0, 1;

Formula

Number triangle T(n, k)=if(k<=n, C(0, n-k)+2*C(1, n-k)-2, 0).
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