OFFSET
1,2
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) = 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)
MAPLE
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 *)
PROG
(Magma) [10*Floor(n/2): n in [1..70]]; // Vincenzo Librandi, Sep 19 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 26 2009
EXTENSIONS
Edited by Rick L. Shepherd, Jun 17 2010
Definition rewritten, using Shepherd's formula, by Vincenzo Librandi, Sep 19 2013
STATUS
approved