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A117439 Expansion of (1-x^2)/(1-4x-2x^2+x^4). 1
1, 4, 17, 76, 337, 1496, 6641, 29480, 130865, 580924, 2578785, 11447508, 50816737, 225581040, 1001378849, 4445229968, 19732860833, 87596322228, 388849631729, 1726145941404, 7662550168241, 34014896233544, 150995835638929 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Row sums of unsigned version of number triangle A117438.

LINKS

Table of n, a(n) for n=0..22.

FORMULA

a(n)=4a(n-1)+2a(n-2)-a(n-4); a(n)=sum{k=0..floor(n/2), C(2n-3k,k)4^(n-2)}.

CROSSREFS

Sequence in context: A255714 A151247 A290914 * A081910 A026773 A081186

Adjacent sequences:  A117436 A117437 A117438 * A117440 A117441 A117442

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Mar 16 2006

STATUS

approved

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Last modified April 22 08:06 EDT 2019. Contains 322329 sequences. (Running on oeis4.)