OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: (1+3x^2+2x^3)/((1-x)^2*(1+x+x^2)).
a(n) = A168075(n)/(-3)^n.
a(n) = A061891(n). - Georg Fischer, Oct 14 2018
MATHEMATICA
LinearRecurrence[{1, 0, 1, -1}, {1, 1, 4, 7}, 50] (* G. C. Greubel, Jul 09 2016 *)
CoefficientList[Series[(1 + 3 x^2 + 2 x^3) / ((1 - x)^2 (1 + x + x^2)), {x, 0, 60}], x] (* Vincenzo Librandi, Jul 10 2016 *)
PROG
(PARI) Vec((1+3*x^2+2*x^3)/((1-x)^2*(1+x+x^2)) + O(x^70)) \\ Michel Marcus, Dec 03 2014
(Magma) I:=[1, 1, 4, 7]; [n le 4 select I[n] else Self(n-1)+Self(n-3)-Self(n-4): n in [1..70]]; // Vincenzo Librandi, Jul 10 2016
CROSSREFS
KEYWORD
dead
AUTHOR
Paul Barry, Nov 18 2009
EXTENSIONS
Corrected by R. J. Mathar, Dec 03 2014
STATUS
approved