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A139800 a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4). 1
1, 0, 0, 0, 2, 2, 4, 8, 18, 34, 68, 136, 274, 546, 1092, 2184, 4370, 8738, 17476, 34952, 69906, 139810, 279620, 559240, 1118482, 2236962, 4473924, 8947848, 17895698, 35791394, 71582788, 143165576, 286331154, 572662306, 1145324612, 2290649224 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

LINKS

Table of n, a(n) for n=0..35.

Index entries for linear recurrences with constant coefficients, signature (1,1,1,2).

FORMULA

a(n)=(3/10-1/10*I)*I^n+(1/3)*(-1)^n+(1/15)*2^n+(3/10+1/10*I)*(-I)^n, with n>=0 and I=(-1)^(1/2) - Paolo P. Lava, Jun 03 2008

O.g.f: (-1+x+x^2+x^3)/((2*x-1)(1+x)(1+x^2)). a(n)=2^n/15+(-1)^n/3+A112030(n)/5. - R. J. Mathar, Jun 12 2008

CROSSREFS

Sequence in context: A108774 A063402 A175195 * A168058 A007971 A126068

Adjacent sequences:  A139797 A139798 A139799 * A139801 A139802 A139803

KEYWORD

nonn

AUTHOR

Paul Curtz, May 22 2008

EXTENSIONS

More terms from R. J. Mathar, Jun 12 2008

STATUS

approved

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Last modified May 28 21:37 EDT 2020. Contains 334690 sequences. (Running on oeis4.)