OFFSET
0,2
COMMENTS
Limit a(n+1)/a(n) = 3+sqrt(8) = 5.82842712...
FORMULA
G.f.: (1-9*x+19*x^2+33*x^3-80*x^4+12*x^5)/(1-12*x+46*x^2-60*x^3+9*x^4).
PROG
(PARI) a(n)=local(A=vector(n+1, r, vector(n+1, c, if(r-1==0 || c-1==0, 1, if(r-1==1, 2*c-1, sum(j=0, c-1, binomial(r+c-j-2, c-j-1)*(binomial(2*r-2, 2*j)-2*(r-1)*binomial(r-3, j-1)))))))); sum(k=0, n, polcoeff(subst(Ser(A[n+1]), x, x/(1+x))/(1+x), k))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul D. Hanna, Jun 10 2005
STATUS
approved