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A113680 Riordan array ((1-x-2x^2)/(1-x),x). 2
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 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

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

LINKS

Table of n, a(n) for n=0..85.

FORMULA

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

EXAMPLE

Triangle begins

1;

0, 1;

-2, 0, 1;

-2, -2, 0, 1;

-2, -2, -2, 0, 1;

-2, -2, -2, -2, 0, 1;

CROSSREFS

Sequence in context: A101663 A284749 A062169 * A316723 A128187 A266477

Adjacent sequences:  A113677 A113678 A113679 * A113681 A113682 A113683

KEYWORD

easy,sign,tabl

AUTHOR

Paul Barry, Nov 04 2005

STATUS

approved

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Last modified August 25 05:45 EDT 2019. Contains 326323 sequences. (Running on oeis4.)