OFFSET
0,2
COMMENTS
Row sums of number triangle A128417.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: 8*x/(sqrt(1-8*x)*(sqrt(1-8*x)+12*x-1));
Conjecture: n^2*a(n)+(12+4*n-17*n^2)*a(n-1) +36*(n+1)*(2*n-3)*a(n-2)=0. - R. J. Mathar, Nov 05 2012
a(n) ~ 2^(3*n+1) / sqrt(Pi*n). - Vaclav Kotesovec, Feb 03 2014
MATHEMATICA
Table[Sum[2^(n-k) Binomial[2n, n-k], {k, 0, n}], {n, 0, 20}] (* Harvey P. Dale, Jan 06 2013 *)
PROG
(PARI) x='x +O('x^50); Vec(8*x/(sqrt(1-8*x)*(sqrt(1-8*x)+12*x-1))) \\ G. C. Greubel, Feb 09 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 02 2007
STATUS
approved