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A176900 sin((2*n+5)*Pi/6)*(n+1)*2^(n+1) 1
1, -4, -24, -32, 80, 384, 448, -1024, -4608, -5120, 11264, 49152, 53248, -114688, -491520, -524288, 1114112, 4718592, 4980736, -10485760, -44040192, -46137344, 96468992, 402653184, 419430400, -872415232, -3623878656, -3758096384 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

From log((1+x)/(1-x+x^2)) at x=1/2,

Sum_{k>=0} 1/a(k) = log(2)

LINKS

Table of n, a(n) for n=0..27.

Index entries for linear recurrences with constant coefficients, signature (4,-12,16,-16).

FORMULA

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

PROG

(PARI) a(n)=[1, -1, -2, -1, 1, 2][n%6+1]*(n+1)*2^n

CROSSREFS

Cf. A002162.

Sequence in context: A144137 A238222 A180924 * A166727 A229295 A007544

Adjacent sequences:  A176897 A176898 A176899 * A176901 A176902 A176903

KEYWORD

sign

AUTHOR

Jaume Oliver Lafont, Apr 28 2010

STATUS

approved

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Last modified January 24 22:09 EST 2021. Contains 340414 sequences. (Running on oeis4.)