a(n) = Sum_{k=0..floor(n/3)} binomial(4*n-3*k-2,n-3*k).
A390706
a(n) = Sum_{k=0..floor(n/3)} binomial(4*n-3*k-2,n-3*k).
Terms
- a(0) =1a(1) =2a(2) =15a(3) =121a(4) =1012a(5) =8673a(6) =75583a(7) =666675a(8) =5933931a(9) =53190814a(10) =479494265a(11) =4342462644a(12) =39478385801a(13) =360077007227
External references
- oeis: A390706