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A161365 a(n) = 3/2 + 5*n - 5*(-1)^n/2. 1
9, 9, 19, 19, 29, 29, 39, 39, 49, 49, 59, 59, 69, 69, 79, 79, 89, 89, 99, 99, 109, 109, 119, 119, 129, 129, 139, 139, 149, 149, 159, 159, 169, 169, 179, 179, 189, 189, 199, 199, 209, 209, 219, 219, 229, 229, 239, 239, 249, 249, 259, 259, 269, 269, 279, 279, 289 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

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

FORMULA

a(n) = 10*n - a(n-1) - 2, n > 1.

a(n+1) = A017377(floor(n/2)). - R. J. Mathar, Jan 05 2011

G.f.: x*(9+x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Jan 05 2011

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {9, 9, 19}, 60] (* Vincenzo Librandi, Mar 02 2012 *)

PROG

(MAGMA) I:=[9, 9, 19]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..60]]; // Vincenzo Librandi, Mar 02 2012

(PARI) for(n=1, 60, print1(3/2+5*n-5*(-1)^n/2", ")); \\ Vincenzo Librandi, Mar 02 2012

CROSSREFS

Sequence in context: A112440 A022092 A245430 * A214831 A197497 A053456

Adjacent sequences:  A161362 A161363 A161364 * A161366 A161367 A161368

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 25 2009

EXTENSIONS

Definition rewritten by R. J. Mathar, Jan 05 2011

STATUS

approved

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Last modified March 19 17:05 EDT 2019. Contains 321330 sequences. (Running on oeis4.)