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
a(n) = A168212(n-1), n>1. - R. J. Mathar, Nov 25 2009
From G. C. Greubel, Jul 19 2016: (Start)
a(n) = (14*n - 7 (-1)^n - 5)/4.
a(n) = a(n-1) + a(n-2) - a(n-3).
G.f.: x*(4 + 3*x^2)/((1+x)*(1 - x)^2).
E.g.f.: (1/4)*(-7 + 12*exp(x) + (14*x - 5)*exp(2*x))*exp(-x). (End)
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {4, 4, 11}, 60] (* Vincenzo Librandi, Feb 28 2012 *)
PROG
(Magma) I:=[4, 4, 11]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..60]]; // Vincenzo Librandi, Feb 28 2012
(PARI) a(n)=([0, 1, 0; 0, 0, 1; -1, 1, 1]^(n-1)*[4; 4; 11])[1, 1] \\ Charles R Greathouse IV, Jul 19 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 24 2009
STATUS
approved