Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #7 Apr 12 2018 18:25:23
%S 1,4,26,176,1204,8273,56967,392688,2708322,18683233,128892764,
%T 889172365,6133354976,42300883471,291696384929,2011120962840,
%U 13863370486596,95548230542403,658416136868846,4536321401562529
%N Sum_{i=0..n} binomial(2n+i,2i).
%F a(n) ~ phi^(4*n + 1) / sqrt(5), where phi = A001622 = (1 + sqrt(5))/2 is the golden ratio. - _Vaclav Kotesovec_, Apr 12 2018
%t Table[Sum[Binomial[2n+i,2i],{i,0,n}],{n,0,20}] (* _Harvey P. Dale_, Apr 12 2018 *)
%K nonn
%O 0,2
%A _Ralf Stephan_, Jun 03 2005