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A138341 Expansion of (1-4x-x^3)/(1-x+x^2)^2. 2
1, -2, -7, -7, 2, 13, 13, -2, -19, -19, 2, 25, 25, -2, -31, -31, 2, 37, 37, -2, -43, -43, 2, 49, 49, -2, -55, -55, 2, 61, 61, -2, -67, -67, 2, 73, 73, -2, -79, -79, 2, 85, 85, -2, -91, -91, 2, 97, 97, -2, -103 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Hankel transform of A079309.

LINKS

Table of n, a(n) for n=0..50.

FORMULA

a(n)=(2n+1)cos(pi*n/3)-(2n+5)*sin(pi*n/3)/sqrt(3);

CROSSREFS

Cf. A138342.

Sequence in context: A159790 A251809 A016639 * A153520 A153649 A020770

Adjacent sequences:  A138338 A138339 A138340 * A138342 A138343 A138344

KEYWORD

easy,sign

AUTHOR

Paul Barry, Mar 15 2008

STATUS

approved

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Last modified February 22 18:31 EST 2019. Contains 320400 sequences. (Running on oeis4.)