0,2

In general a(n)=sum{k=0..floor(n/4), C(n-k,3k)u^k*v^(n-4k)} has g.f. (1-v*x)^2/((1-v*x)^3-u*x^4) and satisfies the recurrence a(n)==3v*a(n-1)-3v^2*a(n-2)+v^3*a(n-3)+u*a(n-4).

G.f.: (1-2x)^2/((1-2x)^3-2x^4); a(n)=6a(n-1)-12a(n-2)+8a(n-3)+2a(n-4).

Cf. A003522, A097119, A099786, A099787.

Sequence in context: A113989 A126757 A034766 this_sequence A135422 A116723 A058374

Adjacent sequences: A099782 A099783 A099784 this_sequence A099786 A099787 A099788

easy,nonn

Paul Barry (pbarry(AT)wit.ie), Oct 26 2004