a(n) = Sum_{k=0..n} binomial(4*n-2*k+1,n-k).
A390413
a(n) = Sum_{k=0..n} binomial(4*n-2*k+1,n-k).
Terms
- a(0) =1a(1) =6a(2) =44a(3) =351a(4) =2925a(5) =25024a(6) =217855a(7) =1920294a(8) =17084132a(9) =153086649a(10) =1379651559a(11) =12491989470a(12) =113548602181
External references
- oeis: A390413