OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
T. Mansour and M. Shattuck, Some enumerative results related to ascent sequences, arXiv preprint arXiv:1207.3755 [math.CO], 2012. Also Discrete Math., 315-316 (2013), 29-41. See Lemma A.2.
Index entries for linear recurrences with constant coefficients, signature (7,-16,13,-2).
FORMULA
G.f.: (1-x)/((1-2*x)*(1-5*x+6*x^2-x^3)).
a(n) = 7*a(n-1)-16*a(n-2)+13*a(n-3)-2*a(n-4) for n>3, a(0)=1, a(1)=6, a(2)=26, a(3)=99. - Philippe Deléham, Dec 25 2013
MATHEMATICA
CoefficientList[Series[(1 - x)/((1 - 2 x) (1 - 5 x + 6 x^2 - x^3)), {x, 0, 40}], x] (* Vincenzo Librandi, Apr 28 2014 *)
PROG
(Magma) I:=[1, 6, 26, 99]; [n le 4 select I[n] else 7*Self(n-1)-16*Self(n-2)+13*Self(n-3)-2*Self(n-4): n in [1..30]]; // Vincenzo Librandi, Apr 28 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Dec 23 2013
STATUS
approved