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A168415 a(n) = 2^n + 7. 9
8, 9, 11, 15, 23, 39, 71, 135, 263, 519, 1031, 2055, 4103, 8199, 16391, 32775, 65543, 131079, 262151, 524295, 1048583, 2097159, 4194311, 8388615, 16777223, 33554439, 67108871, 134217735, 268435463, 536870919, 1073741831, 2147483655 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(n) is prime <=> a(n) is in A104066 <=> n is in A057195 <=> 2^(n-1)*a(n) = A257272(n) is in A125247. - M. F. Hasler, Apr 27 2015

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (3,-2).

FORMULA

a(n) = 2*a(n-1) - 7, n>1.

G.f.: ( 8 - 15*x ) / ( (2*x-1)*(x-1) ). - R. J. Mathar, Jul 10 2011

a(n) = A000079(n) + 7. - Omar E. Pol, Sep 20 2011

E.g.f.: exp(2*x) + 7*exp(x). - G. C. Greubel, Jul 22 2016

MATHEMATICA

a[n_]:=2^n+7; a[Range[0, 200]] (* Vladimir Joseph Stephan Orlovsky, Feb 20 2011*)

CoefficientList[Series[(8 - 15 x)/((2 x - 1) (x - 1)), {x, 0, 200}], x] (* Vincenzo Librandi, Sep 19 2013 *)

LinearRecurrence[{3, -2}, {8, 9}, 40] (* Harvey P. Dale, Mar 03 2014 *)

PROG

(PARI) a(n)=1<<n+7 \\ Charles R Greathouse IV, Sep 20 2011

(MAGMA) [2^n+7: n in [0..40]]; // Vincenzo Librandi, Sep 19 2013

CROSSREFS

Cf. A000079, A057195, A104066, A125247, A257272.

Sequence in context: A120176 A139049 A048590 * A199635 A131864 A179443

Adjacent sequences:  A168412 A168413 A168414 * A168416 A168417 A168418

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Dec 01 2009

STATUS

approved

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Last modified March 28 22:27 EDT 2017. Contains 284249 sequences.