OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.
Index entries for linear recurrences with constant coefficients, signature (3, -2, 0, -1, 1).
FORMULA
G.f.: A(x) = -{x(x^2+x^3+1-x)}/{(x-1)^2(x^3+x^2+x-1)}
a(n)=A000213(n+2)-n-1. [From R. J. Mathar, Aug 05 2008]
a(0)=0, a(1)=1, a(2)=2, then a(n) = a(n-1) + a(n-2) + a(n-3) + 2*n - 4. [From Gerald McGarvey, Oct 06 2009]
MATHEMATICA
LinearRecurrence[{3, -2, 0, -1, 1}, {1, 2, 5, 12, 25}, 40] (* Harvey P. Dale, Jan 21 2016 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
EXTENSIONS
Extended beyond a(30) by R. J. Mathar, Aug 05 2008
STATUS
approved