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A168457 a(n) = (10*n + 5*(-1)^n - 1)/2. 3
2, 12, 12, 22, 22, 32, 32, 42, 42, 52, 52, 62, 62, 72, 72, 82, 82, 92, 92, 102, 102, 112, 112, 122, 122, 132, 132, 142, 142, 152, 152, 162, 162, 172, 172, 182, 182, 192, 192, 202, 202, 212, 212, 222, 222, 232, 232, 242, 242, 252, 252, 262, 262, 272, 272, 282 (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) - 6 for n>1, a(1)=2.

From Bruno Berselli, Sep 16 2013: (Start)

G.f.: 2*x*(1 + 5*x - x^2)/((1+x)*(1-x)^2).

a(n) = A168459(n) + 1 = 2*A168282(n).

a(n) = a(n-1) +a(n-2) -a(n-3). (End)

a(n) = 2 + 10*Floor(n/2). -  Vincenzo Librandi, Sep 19 2013

E.g.f.: (1/2)*(5 - 4*exp(x) + (10*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 22 2016

MATHEMATICA

Table[5 n + 5 (-1)^n/2 - 1/2, {n, 60}] (* Bruno Berselli, Sep 16 2013 *)

Table[2 + 10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[2 (1 + 5 x - x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *)

PROG

(MAGMA) [2+10*Floor(n/2): n in [1..70]]; // Vincenzo Librandi, Sep 19 2013

CROSSREFS

Cf. A017293, A168459, A168282.

Sequence in context: A171446 A068515 A088240 * A045895 A251421 A226393

Adjacent sequences:  A168454 A168455 A168456 * A168458 A168459 A168460

KEYWORD

nonn,easy,less

AUTHOR

Vincenzo Librandi, Nov 26 2009

EXTENSIONS

New definition by Bruno Berselli, Sep 16 2013

STATUS

approved

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Last modified October 26 05:34 EDT 2021. Contains 348256 sequences. (Running on oeis4.)