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A106509 Riordan array ((1+x)/(1+x+x^2),x/(1+x)) read by rows. 3
1, 0, 1, -1, -1, 1, 1, 0, -2, 1, 0, 1, 2, -3, 1, -1, -1, -1, 5, -4, 1, 1, 0, 0, -6, 9, -5, 1, 0, 1, 0, 6, -15, 14, -6, 1, -1, -1, 1, -6, 21, -29, 20, -7, 1, 1, 0, -2, 7, -27, 50, -49, 27, -8, 1, 0, 1, 2, -9, 34, -77, 99, -76, 35, -9, 1, -1, -1, -1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,9

COMMENTS

Row sums are A106510. Diagonal sums are A106511. Inverse of A072405 (when this starts 1,0,1,...).

LINKS

Table of n, a(n) for n=0..68.

FORMULA

Number triangle T(n, k)=sum{j=0..n-k, (-1)^j*binomial(2n-k-j, j)}

T(n,k) = T(n-1,k-1)-2*T(n-1,k)+T(n-2,k-1)-2*T(n-2,k)+T(n-3,k-1)-T(n-3,k), T(0,0)=T(1,1)=T(2,2)=1, T(1,0)=0, T(2,1)=T(2,0)=-1, T(n,k)=0 if k<0 or if k>n. - Philippe Deléham, Jan 12 2014

EXAMPLE

Triangle begins

1;

0,1;

-1,-1,1;

1,0,-2,1;

0,1,2,-3,1;

-1,-1,-1,5,-4,1;

CROSSREFS

Sequence in context: A119339 A037835 A116433 * A228110 A196199 A053615

Adjacent sequences:  A106506 A106507 A106508 * A106510 A106511 A106512

KEYWORD

easy,sign,tabl

AUTHOR

Paul Barry, May 04 2005

STATUS

approved

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Last modified April 20 16:29 EDT 2014. Contains 240807 sequences.