0,4

Form a graph from a triangle and its midpoint triangle. A093043 counts walks of length n between two vertices of the original triangle.

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

Sequence in context: A115240 A027989 A096483 this_sequence A061566 A082398 A053156

Adjacent sequences: A093040 A093041 A093042 this_sequence A093044 A093045 A093046

easy,nonn

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