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A168413 a(n) = 9*n - a(n-1) - 5, with a(1)=2. 1
2, 11, 11, 20, 20, 29, 29, 38, 38, 47, 47, 56, 56, 65, 65, 74, 74, 83, 83, 92, 92, 101, 101, 110, 110, 119, 119, 128, 128, 137, 137, 146, 146, 155, 155, 164, 164, 173, 173, 182, 182, 191, 191, 200, 200, 209, 209, 218, 218, 227, 227, 236, 236, 245, 245, 254, 254 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..5000

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

a(n) = (18*n + 9*(-1)^n - 1)/4, with n>=1. - Paolo P. Lava, Nov 27 2009

G.f.: x*(2 + 9*x - 2*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Jul 10 2011

E.g.f.: (1/4)*(9 - 8*exp(x) + (18*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 22 2016

EXAMPLE

For n=2, a(2)=9*2-2-5=11; n=3, a(3)=9*3-11-5=11; n=4, a(4)=9*4-11-5=20.

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {2, 11, 11}, 50] (* G. C. Greubel, Jul 22 2016 *)

PROG

(MAGMA) [-(1/4)+(9/4)*(-1)^n+(9/2)*n: n in [1..60]]

CROSSREFS

Cf. A017186.

Sequence in context: A027828 A106371 A145523 * A265561 A265545 A153705

Adjacent sequences:  A168410 A168411 A168412 * A168414 A168415 A168416

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 25 2009

STATUS

approved

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Last modified September 22 00:25 EDT 2017. Contains 292326 sequences.