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A104565 Reversion of Pell numbers A000129(n+1). 1
1, -2, 3, -2, -6, 28, -61, 54, 158, -860, 2062, -2004, -5804, 33720, -84509, 86054, 247862, -1492908, 3838298, -4019452, -11537556, 71101832, -185868978, 198310460, 567902572, -3555617432, 9404104764, -10168382696, -29069700056, 184127171952, -491229517661 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

FORMULA

G.f.: (sqrt(1+4x+8x^2)-1-2x)/(2x^2).

a(n)=sum{k=0..floor(n/2), binomial(n, 2k)*C(k)*(-1)^(n-k)2^(n-2k)}, where C(n) is A000108. - Paul Barry (pbarry(AT)wit.ie), May 16 2005

CROSSREFS

Sequence in context: A188881 A143806 A109878 * A144456 A051886 A180916

Adjacent sequences:  A104562 A104563 A104564 * A104566 A104567 A104568

KEYWORD

easy,sign

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Mar 15 2005

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Last modified February 17 00:09 EST 2012. Contains 205978 sequences.