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A168329 a(n) = (3/2)*(2*n - (-1)^n - 1). 4
3, 3, 9, 9, 15, 15, 21, 21, 27, 27, 33, 33, 39, 39, 45, 45, 51, 51, 57, 57, 63, 63, 69, 69, 75, 75, 81, 81, 87, 87, 93, 93, 99, 99, 105, 105, 111, 111, 117, 117, 123, 123, 129, 129, 135, 135, 141, 141, 147, 147, 153, 153, 159, 159, 165, 165, 171, 171, 177, 177, 183, 183 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

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

FORMULA

a(n) = 6*n - a(n-1) - 6 for n>1, a(1)=3.

G.f.: 3*x*(1 + x^2)/((1+x)*(1-x)^2). - Bruno Berselli, Nov 06 2011

a(n) = -a(-n+1) = 3*A109613(n-1) = A198392(n-1) - A198392(-n). - Bruno Berselli, Nov 06 2011 - Sep 17 2013

E.g.f.: (3/2)*(-1 + 2*exp(x) + (2*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 18 2016

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {3, 3, 9}, 80 ] (* Vincenzo Librandi, Nov 15 2011 *)

Table[(3/2) (2 n - (-1)^n - 1), {n, 70}] (* Bruno Berselli, Sep 17 2013 *)

PROG

(MAGMA) [(3/2)*(2*n-(-1)^n-1): n in [1..70]] // Vincenzo Librandi, Nov 15 2011

CROSSREFS

Cf. A016945, A109613.

Sequence in context: A107443 A204099 A062234 * A161828 A219128 A217964

Adjacent sequences:  A168326 A168327 A168328 * A168330 A168331 A168332

KEYWORD

nonn,easy,less

AUTHOR

Vincenzo Librandi, Nov 23 2009

EXTENSIONS

New definition by Bruno Berselli, Sep 17 2013

STATUS

approved

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Last modified October 21 01:15 EDT 2019. Contains 328291 sequences. (Running on oeis4.)