A168284 a(n) = (10*n + 5*(-1)^n - 5)/4.

0, 5, 5, 10, 10, 15, 15, 20, 20, 25, 25, 30, 30, 35, 35, 40, 40, 45, 45, 50, 50, 55, 55, 60, 60, 65, 65, 70, 70, 75, 75, 80, 80, 85, 85, 90, 90, 95, 95, 100, 100, 105, 105, 110, 110, 115, 115, 120, 120, 125, 125, 130, 130, 135, 135, 140, 140, 145, 145, 150, 150, 155

Offset

1,2

Comments

a(n) = A166598(n-1) for n > 1. - Georg Fischer, Oct 14 2018

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) = 5*n - a(n-1) - 5, with n > 1, a(1)=0.

G.f.: 5*x^2/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 16 2013

a(n) = 5*A004526(n). - Bruno Berselli, Sep 17 2013

E.g.f.: (5/4)*(1 + (2*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 17 2016

Mathematica

CoefficientList[Series[5 x/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 16 2013 *)
Table[5 n/2 + 5 (-1)^n/4 - 5/4, {n, 70}] (* Bruno Berselli, Sep 17 2013 *)

Prog

(Magma) [n le 1 select (n-1) else 5*n-Self(n-1)-5: n in [1..70]]; // Vincenzo Librandi, Sep 16 2013

Crossrefs

Cf. A004526, A008587.

Sequence in context: A341831 A360996 A003882 * A166598 A066256 A029842

Adjacent sequences: A168281 A168282 A168283 * A168285 A168286 A168287

Keyword

nonn,easy,less

Author

Vincenzo Librandi, Nov 22 2009

Extensions

New definition by Bruno Berselli, Sep 17 2013

Status

approved