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Search: id:A087205
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A087205 a(n)=-2a(n-1)+4a(n-2), a(0)=1,a(1)=2. +0
2
1, 2, 0, 8, -16, 64, -192, 640, -2048, 6656, -21504, 69632, -225280, 729088, -2359296, 7634944, -24707072, 79953920, -258736128, 837287936, -2709520384, 8768192512, -28374466560, 91821703168, -297141272576, 961569357824, -3111703805952 (list; graph; listen)
OFFSET

0,2

COMMENT

Inverse binomial transform of A087204. a(n+2)=A085449(n)*(-1)^(n+1); a(n+3)=A063727(n)*(-1)^n.

FORMULA

a(n)=(-1-sqrt(5))^n(1/2-3sqrt(5)/10)+(-1+sqrt(5))^n(1/2+3sqrt(5)/10).

CROSSREFS

Cf. A084222.

Sequence in context: A120559 A120555 A128063 this_sequence A062134 A002909 A118437

Adjacent sequences: A087202 A087203 A087204 this_sequence A087206 A087207 A087208

KEYWORD

easy,sign

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Aug 25 2003

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Last modified December 7 08:40 EST 2009. Contains 170430 sequences.


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