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A029745 Expansion of (1+2x+6x^2+x^3)/(1-2x^2). 1
1, 2, 8, 5, 16, 10, 32, 20, 64, 40, 128, 80, 256, 160, 512, 320, 1024, 640, 2048, 1280, 4096, 2560, 8192, 5120, 16384, 10240, 32768, 20480, 65536, 40960, 131072, 81920, 262144, 163840, 524288, 327680, 1048576, 655360, 2097152, 1310720, 4194304 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Note that 4 is the only power of 2 not here. All terms are either 2^k or 5*2^k.

Note that 4 is the only power of 2 not here. All terms are either 2^k or 5*2^k.

LINKS

Table of n, a(n) for n=1..41.

Index entries for linear recurrences with constant coefficients, signature (0,2)

FORMULA

G.f.: (1+2x+6x^2+x^3)/(1-2x^2).

MATHEMATICA

LinearRecurrence[{0, 2}, {1, 2, 8, 5}, 50] (* or *) With[{nn=20}, Join[{1, 2}, Riffle[ 8*2^Range[0, nn], 5 2^Range[0, nn]]]] (* Harvey P. Dale, Sep 28 2016 *)

PROG

(PARI) a(n)=if(n<2, 1+max(-1, n), 2^(n\2)*if(n%2, 5/2, 4))

CROSSREFS

Cf. A094958 (numbers of the form 2^n or 5*2^n)

Sequence in context: A182528 A185583 A155901 * A183232 A096417 A274416

Adjacent sequences:  A029742 A029743 A029744 * A029746 A029747 A029748

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Edited by T. D. Noe, Nov 12 2010

STATUS

approved

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Last modified November 20 00:42 EST 2017. Contains 294957 sequences.