A166544 a(n) = 7*n - a(n-1), with n>1, a(1)=2.

2, 12, 9, 19, 16, 26, 23, 33, 30, 40, 37, 47, 44, 54, 51, 61, 58, 68, 65, 75, 72, 82, 79, 89, 86, 96, 93, 103, 100, 110, 107, 117, 114, 124, 121, 131, 128, 138, 135, 145, 142, 152, 149, 159, 156, 166, 163, 173, 170, 180, 177, 187, 184, 194, 191, 201, 198, 208, 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

G.f.: -x*(-2-10*x+5*x^2)/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 13 2013

From G. C. Greubel, May 17 2016: (Start)

E.g.f.: (1/4)*(7*(1 + 2*x)*exp(x) + 13*exp(-x) - 20).

a(n) = a(n-1) + a(n-2) - a(n-3). (End)

Sum_{n>=1} (-1)^(n+1)/a(n) = 1/5 + tan(3*Pi/14)*Pi/7. - Amiram Eldar, Feb 23 2023

Mathematica

CoefficientList[Series[-(- 2 - 10 x + 5 x^2)/((1 + x) (x - 1)^2), {x, 0, 80}], x] (* Vincenzo Librandi, Sep 13 2013 *)
LinearRecurrence[{1, 1, -1}, {2, 12, 9}, 50] (* G. C. Greubel, May 17 2016 *)

Prog

(Magma) [n eq 1 select 2 else 7*n-Self(n-1): n in [1..80]]; // Vincenzo Librandi, Sep 13 2013

Crossrefs

Sequence in context: A229628 A002209 A100654 * A081468 A216349 A280015

Adjacent sequences: A166541 A166542 A166543 * A166545 A166546 A166547

Keyword

nonn,easy

Author

Vincenzo Librandi, Oct 16 2009

Status

approved