0,4

Form a graph from a triangle and its midpoint triangle. A093042 counts walks of length n between a vertex of the original triangle and an adjacent vertex of the midpoint triangle.

G.f.: (1-2x^2)/((1+x-x^2)(1-2x-4x^2)); a(n)=A001045(n)*A000045(n); a(n) := (2^n/3-(-1)^n/3)(((1+sqrt(5))/2)^n/sqrt(5)-((1-sqrt(5))/2)^n/sqrt(5)).

Sequence in context: A122365 A119132 A073065 this_sequence A067665 A012595 A012294

Adjacent sequences: A093039 A093040 A093041 this_sequence A093043 A093044 A093045

easy,nonn

Paul Barry (pbarry(AT)wit.ie), Mar 22 2004