OFFSET
0,2
COMMENTS
a(n)/a(n-1) tends to -3.
LINKS
FORMULA
a(0)=1, a(1)=3, a(n)=3*a(n-2)-2*a(n-1).
G.f.: (1+5x)/(1+2x-3x^2).
a(n)= Sum_{k=0..n} A112555(n,k)*2^(n-k).
MATHEMATICA
3/2*(1 + (-3)^(Range[0, 29] - 1)) (* or *)
LinearRecurrence[{-2, 3}, {1, 3}, 30] (* Paolo Xausa, Apr 22 2024 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Philippe Deléham, Sep 21 2009
STATUS
approved