0,4

G.f.: (1-2x+x^2)/(1-3x+3x^2-6x^3); a(n)=3a(n-1)-3a(n-2)+6a(n-3); a(n)=sum{k=0..floor(n/3), binomial(n, 3k)5^k }.

Sequence in context: A087863 A051941 A028345 this_sequence A135454 A069778 A015644

Adjacent sequences: A097121 A097122 A097123 this_sequence A097125 A097126 A097127

easy,nonn

Paul Barry (pbarry(AT)wit.ie), Jul 25 2004