a(n) = 1/16*{-2+[9+4*sqrt(5)]^n+[9-4*sqrt(5)]^n}. - R. Stephan, Apr 14 2004
a(n)=(T(n, 9)-1)/8 with Chebyshev's polynomials of the first kind evaluated at x=9: T(n, 9)=A023039(n). W. Lang (wolfdieter.lang_AT_physik_DOT_uni-karlsruhe_DOT_de), Oct 18 2004
G.f.: x*(1+x)/((1-x)*(1-18*x+x^2)) = x*(1+x)/(1-19*x+19*x^2-x^3) (from the Stephan link, see A092184).
