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A168379 a(n) = 4*n - 2*(-1)^n + 1. 2
7, 7, 15, 15, 23, 23, 31, 31, 39, 39, 47, 47, 55, 55, 63, 63, 71, 71, 79, 79, 87, 87, 95, 95, 103, 103, 111, 111, 119, 119, 127, 127, 135, 135, 143, 143, 151, 151, 159, 159, 167, 167, 175, 175, 183, 183, 191, 191, 199, 199, 207, 207, 215, 215, 223, 223, 231, 231 (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) = 8*n - a(n-1) - 2, with n>1, a(1)=7.

a(n) = 1 - 2*(-1)^n + 4*n. - Paolo P. Lava, Nov 27 2009

G.f.: x*(7 + x^2)/((1+x)*(1-x)^2). - Vincenzo Librandi, Sep 18 2013

a(n) = a(n-1) +a(n-2) -a(n-3). - Vincenzo Librandi, Sep 18 2013

a(n) = 7 + 8*floor((n-1)/2). - Bruno Berselli, Sep 18 2013

E.g.f.: (-2 + exp(x) + (4*x + 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 19 2016

MAPLE

A168379:=n->4*n - 2*(-1)^n + 1: seq(A168379(n), n=1..100); # Wesley Ivan Hurt, Apr 26 2017

MATHEMATICA

Table[4 n - 2 (-1)^n + 1, {n, 60}] (* Bruno Berselli, Sep 18 2013 *)

CoefficientList[Series[(7 + x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 18 2013 *)

PROG

(MAGMA) [4*n -2*(-1)^n + 1: n in [1..70]]; // Vincenzo Librandi, Sep 18 2013

CROSSREFS

Sequence in context: A112438 A022090 A245426 * A179886 A214829 A168411

Adjacent sequences:  A168376 A168377 A168378 * A168380 A168381 A168382

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 24 2009

EXTENSIONS

Definition rewritten, using Lava's formula, by Vincenzo Librandi, Sep 18 2013

STATUS

approved

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Last modified June 15 20:50 EDT 2019. Contains 324145 sequences. (Running on oeis4.)