A168333 a(n) = (14*n + 7*(-1)^n + 1)/4.

2, 9, 9, 16, 16, 23, 23, 30, 30, 37, 37, 44, 44, 51, 51, 58, 58, 65, 65, 72, 72, 79, 79, 86, 86, 93, 93, 100, 100, 107, 107, 114, 114, 121, 121, 128, 128, 135, 135, 142, 142, 149, 149, 156, 156, 163, 163, 170, 170, 177, 177, 184, 184, 191, 191, 198, 198, 205, 205

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) - 3, with n>1, a(1)=2.

G.f.: x*(2 + 7*x - 2*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) = A168331(n) - 1 = A168337(n) + 1 = A168212(n) - 2 = A168374(n) + 2. - Bruno Berselli, Sep 17 2013

E.g.f.: (1/4)*(7 - 8*exp(x) + (14*x + 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 18 2016

Mathematica

CoefficientList[Series[(2 + 7 x - 2 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 17 2013 *)
LinearRecurrence[{1, 1, -1}, {2, 9, 9}, 70] (* Harvey P. Dale, Mar 13 2014 *)

Prog

(Magma) [n eq 1 select 2 else 7*n-Self(n-1)-3: n in [1..70]]; // Vincenzo Librandi, Sep 17 2013

Crossrefs

Cf. A017005, A168212, A168331, A168337, A168374.

Sequence in context: A331369 A197394 A198942 * A238412 A242064 A109322

Adjacent sequences: A168330 A168331 A168332 * A168334 A168335 A168336

Keyword

nonn,easy,less

Author

Vincenzo Librandi, Nov 23 2009

Extensions

New definition by Bruno Berselli, Sep 17 2013

Status

approved