A168336 a(n) = 5 + 7*floor((n-1)/2).

5, 5, 12, 12, 19, 19, 26, 26, 33, 33, 40, 40, 47, 47, 54, 54, 61, 61, 68, 68, 75, 75, 82, 82, 89, 89, 96, 96, 103, 103, 110, 110, 117, 117, 124, 124, 131, 131, 138, 138, 145, 145, 152, 152, 159, 159, 166, 166, 173, 173, 180, 180, 187, 187, 194, 194, 201, 201, 208

Offset: 1

Author

Vincenzo Librandi, Nov 23 2009

Keywords

• nonn
• easy
• less

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. A017041, A168332, A168373.

Programs

Magma

[5+7*Floor((n-1)/2): n in [1..70]]; // Vincenzo Librandi, Sep 18 2013

Mathematica

Table[5 + 7 Floor[(n - 1)/2], {n, 60}] (* Bruno Berselli, Sep 18 2013 *)
CoefficientList[Series[(5 + 2 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 18 2013 *)

Formula

a(n) = 7*n - a(n-1) - 4, with n>1, a(1)=5.

G.f.: x*(5 + 2*x^2)/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 18 2013

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

a(n) = (14*n - 7*(-1)^n - 1)/4. - Bruno Berselli, Sep 18 2013

a(n) = A168332(n) - 1 = A168373(n) + 1. - Bruno Berselli, Sep 18 2013

E.g.f.: (1/2)*(4 + (7*x - 4)*cosh(x) + (7*x + 3)* sinh(x)). - G. C. Greubel, Jul 18 2016

Extensions

New definition by Vincenzo Librandi, Sep 18 2013