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A175805 a(n) = 21*2^n. 9
21, 42, 84, 168, 336, 672, 1344, 2688, 5376, 10752, 21504, 43008, 86016, 172032, 344064, 688128, 1376256, 2752512, 5505024, 11010048, 22020096, 44040192, 88080384, 176160768, 352321536, 704643072, 1409286144, 2818572288, 5637144576, 11274289152, 22548578304, 45097156608 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

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

FORMULA

G.f.: 21/(1-2*x).

a(n) = 2*a(n-1). - Vincenzo Librandi, Jul 08 2016

MATHEMATICA

Table[21 2^n, {n, 0, 40}] (* Vincenzo Librandi, Jul 08 2016 *)

PROG

(MAGMA)[21*2^n: n in [0..100]]

(PARI) a(n)=21<<n \\ Charles R Greathouse IV, Oct 07 2015

CROSSREFS

Cf. A159256.

Sequence in context: A001682 A180963 A078440 * A039344 A043167 A043947

Adjacent sequences:  A175802 A175803 A175804 * A175806 A175807 A175808

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Dec 05 2010

STATUS

approved

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Last modified November 19 14:52 EST 2018. Contains 317352 sequences. (Running on oeis4.)