OFFSET
0,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,1,-2,-1).
FORMULA
From Philippe Deléham, Dec 28 2013: (Start)
G.f.: (1+x-x^2)/(1-x-x^2)^2.
a(n) = 2*a(n-1) + a(n-2) - 2*a(n-3) - a(n-4), a(0)=1, a(1)=3, a(2)=6, a(3)=13.
a(n) = a(n-1) + a(n-2) + 2*Fibonacci(n). (End)
EXAMPLE
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson, Jul 27 2007
STATUS
approved