A117355 - OEIS

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A117355

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

1, 0, 1, 1, 0, 1, 0, 0, 0, 1, 1, 0, -1, 0, 1, 0, -1, 0, -2, 0, 1, 1, 0, -2, 0, -3, 0, 1, 0, -2, 0, -2, 0, -4, 0, 1, 1, 0, -2, 0, -1, 0, -5, 0, 1, 0, -3, 0, 0, 0, 1, 0, -6, 0, 1, 1, 0, -1, 0, 3, 0, 4, 0, -7, 0, 1, 0, -4, 0, 3, 0, 6, 0, 8, 0, -8, 0, 1, 1, 0, 1, 0, 6, 0, 8, 0, 13, 0, -9, 0, 1

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

0,19

COMMENTS

Row sums are A077948.

Diagonal sums are the aerated version of A009545 with g.f. 1/(1-2x^2+2x^4).

LINKS

Table of n, a(n) for n=0..90.

FORMULA

Number triangle T(n,k)=sum{j=0..n-k, C(j-(n-k)/2-1,j)C(k,j)(1+(-1)^(n-k))/2}

T(n,k)=T(n-1,k-1)+T(n-2,k)-2*T(n-3,k-1), T(0,0)=T(1,1)=T(2,0)=T(2,2)=1, T(1,1)=T(2,1)=0, T(n,k)=0 if k<0 or if k>n. - Philippe Deléham, Jan 16 2014

EXAMPLE

Triangle begins

0, 1,

1, 0, 1,

0, 0, 0, 1,

1, 0, -1, 0, 1,

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

1, 0, -2, 0, -3, 0, 1,

0, -2, 0, -2, 0, -4, 0, 1

CROSSREFS

Sequence in context: A281272 A147310 A025886 * A319571 A086966 A140080

Adjacent sequences: A117352 A117353 A117354 * A117356 A117357 A117358

KEYWORD

easy,sign,tabl

AUTHOR

Paul Barry, Mar 09 2006

STATUS

approved