OFFSET
1,2
LINKS
Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
G.f.: A(x) = -{x(x^4+2x^3+2x^2-x+1)}/{(x-1)^3}
For n >= 3, a(n) = (5n^2 - 21n + 28)/2. - Franklin T. Adams-Watters, Sep 16 2006
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved