



9, 36, 144, 576, 2304, 9216, 36864, 147456, 589824, 2359296, 9437184, 37748736, 150994944, 603979776, 2415919104, 9663676416, 38654705664, 154618822656, 618475290624, 2473901162496, 9895604649984, 39582418599936, 158329674399744, 633318697598976
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OFFSET

0,1


COMMENTS

a(n) is twice the area of the trapezoid created by the four points (2^n,2^(n+1)), (2^(n+1), 2^n), (2^(n+1), 2^(n+2)), (2^(n+2), 2^(n+1)).  J. M. Bergot, May 23 2014


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..500
Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
Tanya Khovanova, Recursive Sequences
Index to sequences with linear recurrences with constant coefficients, signature (4).


FORMULA

a(n)=4*a(n1), n>0; a(0)=9. G.f.: 9/(14*x).  Philippe Deléham, Nov 23 2008


MATHEMATICA

9*4^Range[0, 100] (* Vladimir Joseph Stephan Orlovsky, Jun 09 2011 *)


PROG

(MAGMA) [9*4^n: n in [0..30]]; // Vincenzo Librandi, May 19 2011
(PARI) a(n)=9<<n \\ Charles R Greathouse IV, Apr 17 2012


CROSSREFS

Essentially the same as A055841. First differences of A002001.
Sequence in context: A023872 A034557 A231431 * A075674 A245416 A110752
Adjacent sequences: A002060 A002061 A002062 * A002064 A002065 A002066


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


STATUS

approved



