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A175805
a(n) = 21*2^n.
20
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
OFFSET
0,1
COMMENTS
The squares of these terms appear in A159256. - Elmo R. Oliveira, Sep 15 2024
FORMULA
G.f.: 21/(1-2*x).
a(n) = 2*a(n-1). - Vincenzo Librandi, Jul 08 2016
From Elmo R. Oliveira, Sep 14 2024: (Start)
E.g.f.: 21*exp(2*x).
a(n) = 21*A000079(n). (End)
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
Sequence in context: A180963 A355406 A078440 * A039344 A043167 A043947
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Dec 05 2010
STATUS
approved