OFFSET
0,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..645
FORMULA
a(n)=sum(C(k)*9^k, k=0..n), n>=0, with C(n):=A000108(n).
G.f.: c(9*x)/(1-x), where c(x):=(1-sqrt(1-4*x))/(2*x) is the o.g.f. of Catalan numbers A000108.
Conjecture: +(n+1)*a(n) +(-37*n+17)*a(n-1) +18*(2*n-1)*a(n-2)=0. - R. J. Mathar, Jun 08 2016
MATHEMATICA
Accumulate[Table[CatalanNumber[n]9^n, {n, 0, 20}]] (* Harvey P. Dale, Jun 22 2016 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Oct 31 2005
STATUS
approved