A168461 a(n) = 10*floor(n/2).
0, 10, 10, 20, 20, 30, 30, 40, 40, 50, 50, 60, 60, 70, 70, 80, 80, 90, 90, 100, 100, 110, 110, 120, 120, 130, 130, 140, 140, 150, 150, 160, 160, 170, 170, 180, 180, 190, 190, 200, 200, 210, 210, 220, 220, 230, 230, 240, 240, 250, 250, 260, 260, 270, 270, 280
Offset: 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).
Crossrefs
Programs
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Magma
[10*Floor(n/2): n in [1..70]]; // Vincenzo Librandi, Sep 19 2013
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Maple
A168461:=n->10*floor(n/2); seq(A168461(n), n=1..100); # Wesley Ivan Hurt, Nov 25 2013
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Mathematica
Table[10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[10 x/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *) LinearRecurrence[{1,1,-1},{0,10,10},60] (* Harvey P. Dale, Mar 02 2024 *)
Formula
a(n) = 10*n - a(n-1) - 10, with n>1, a(1)=0.
a(n) = 10*floor(n/2) = A168437(n) - 3. - Rick L. Shepherd, Jun 17 2010
G.f.: 10*x^2/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 19 2013
a(n) = a(n-1) +a(n-2) -a(n-3). - Vincenzo Librandi, Sep 19 2013
From G. C. Greubel, Jul 23 2016: (Start)
a(n) = (5/2)*(2*n + (-1)^n - 1).
E.g.f.: (5/2)*(1 +(2*x - 1)*exp(2*x))*exp(-x). (End)
Extensions
Edited by Rick L. Shepherd, Jun 17 2010
Definition rewritten, using Shepherd's formula, by Vincenzo Librandi, Sep 19 2013