A168332 a(n) = 6 + 7 * floor((n-1)/2).

6, 6, 13, 13, 20, 20, 27, 27, 34, 34, 41, 41, 48, 48, 55, 55, 62, 62, 69, 69, 76, 76, 83, 83, 90, 90, 97, 97, 104, 104, 111, 111, 118, 118, 125, 125, 132, 132, 139, 139, 146, 146, 153, 153, 160, 160, 167, 167, 174, 174, 181, 181, 188, 188, 195, 195, 202, 202, 209

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) = 7*n - a(n-1) - 2, with n>1, a(1)=6.

G.f.: x*(6 + x^2)/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 17 2013

a(n) = a(n-1) +a(n-2) -a(n-3). - Vincenzo Librandi, Sep 17 2013

a(n) = (14*n - 7*(-1)^n + 3)/4 = A168374(n+1) - 1 = A168336(n) + 1. - Bruno Berselli, Sep 17 2013

E.g.f.: (1/2)*(2 + (7*x - 2)*cosh(x) + (7*x + 5)*sinh(x)). - G. C. Greubel, Jul 18 2016

Mathematica

Table[6 + 7 Floor[(n - 1)/2], {n, 60}] (* Bruno Berselli, Sep 17 2013 *)
CoefficientList[Series[(6 + x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 17 2013 *)
LinearRecurrence[{1, 1, -1}, {6, 6, 13}, 60] (* or *) With[{c=NestList[ #+7&, 6, 30]}, Riffle[c, c]] (* Harvey P. Dale, Aug 29 2015 *)

Prog

(Magma) [n eq 1 select 6 else 7*n-Self(n-1)-2: n in [1..70]]; // Vincenzo Librandi, Sep 17 2013

Crossrefs

Cf. A168336, A168374.

Sequence in context: A262850 A262849 A115014 * A214828 A229828 A141378

Adjacent sequences: A168329 A168330 A168331 * A168333 A168334 A168335

Keyword

nonn,easy

Author

Vincenzo Librandi, Nov 23 2009

Extensions

Definition reformulated by Bruno Berselli at the suggestion of Joerg Arndt and using its formula, Sep 17 2013

Status

approved