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
From R. J. Mathar, Nov 22 2009: (Start)
a(n) = a(n-1) + a(n-2) - a(n-3) = n + 1 - 3*(-1)^n.
G.f.: x*(5+2*x^2-5*x)/((1+x)*(x-1)^2). (End)
a(n) = n - 4 + 2^(2-(-1)^n). - Wesley Ivan Hurt, Dec 13 2013
Sum_{n>=3} (-1)^n/a(n) = 23/15 - log(2). - Amiram Eldar, Feb 23 2023
MAPLE
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {5, 0, 7}, 30] (* Vincenzo Librandi, Feb 27 2012 *)
PROG
(Magma) I:=[5, 0, 7]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..40]]; // Vincenzo Librandi, Feb 27 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 20 2009
STATUS
approved