A168463 a(n) = 5 + 11*floor(n/2).

5, 16, 16, 27, 27, 38, 38, 49, 49, 60, 60, 71, 71, 82, 82, 93, 93, 104, 104, 115, 115, 126, 126, 137, 137, 148, 148, 159, 159, 170, 170, 181, 181, 192, 192, 203, 203, 214, 214, 225, 225, 236, 236, 247, 247, 258, 258, 269, 269, 280, 280, 291, 291, 302, 302, 313

Offset: 1

Author

Vincenzo Librandi, Nov 26 2009

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

Crossrefs

Cf. A017449.

Programs

Magma

[5+11*Floor(n/2): n in [1..70]]; // Vincenzo Librandi, Sep 19 2013

Mathematica

Table[5 + 11 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[(5 + 11 x - 5 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *)
LinearRecurrence[{1,1,-1},{5,16,16},80] (* Harvey P. Dale, Aug 28 2019 *)

Formula

a(n) = 11*n - a(n-1) - 1, with n>1, a(1)=5.

G.f.: x*(5 + 11*x - 5*x^2)/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 19 2013

a(n) = a(n-1) +a(n-2) -a(n-3). - Vincenzo Librandi, Sep 19 2013

From G. C. Greubel, Jul 23 2016: (Start)

a(n) = (22*n + 11*(-1)^n + 9)/4.

E.g.f.: (1/4)*(11 - 20*exp(x) + (22*x + 9)*exp(2*x))*exp(-x). (End)

Extensions

New definition by Vincenzo Librandi, Sep 19 2013