A168331 a(n) = (5 + 14*n + 7*(-1)^n)/4.

3, 10, 10, 17, 17, 24, 24, 31, 31, 38, 38, 45, 45, 52, 52, 59, 59, 66, 66, 73, 73, 80, 80, 87, 87, 94, 94, 101, 101, 108, 108, 115, 115, 122, 122, 129, 129, 136, 136, 143, 143, 150, 150, 157, 157, 164, 164, 171, 171, 178, 178, 185, 185, 192, 192, 199, 199, 206, 206

Offset: 1

Author

Vincenzo Librandi, Nov 23 2009

Keywords

• nonn
• easy
• less

Comments

Essentially the same as A168376.

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. A017017, A168376.

Programs

Magma

[5/4+7*n/2+7*(-1)^n/4: n in [1..70]]; // Vincenzo Librandi, Sep 17 2013

Maple

A168331:=n->(5+14*n+7*(-1)^n)/4: seq(A168331(n), n=1..100); # Wesley Ivan Hurt, May 03 2017

Mathematica

Table[5/4 + 7n/2 + 7 (-1)^n/4, {n,60}] (* or *) LinearRecurrence[{1, 1, -1}, {3, 10, 10}, 60] (* Harvey P. Dale, Oct 24 2011 *)
CoefficientList[Series[- (- 3 - 7 x + 3 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 17 2013 *)

Formula

a(n) = 7*n - a(n-1) - 1, with n > 1, a(1)=3.

G.f.: x*(3+7*x-3*x^2) / ((1+x)*(x-1)^2). - R. J. Mathar, Jan 05 2011

a(1)=3, a(2)=10, a(3)=10; for n>3, a(n) = a(n-1)+a(n-2)-a(n-3). - Harvey P. Dale, Oct 24 2011

E.g.f.: (1/4)*(7 - 12*exp(x) + (5 + 14*x)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 18 2016

Extensions

New definition by R. J. Mathar, Jan 05 2011