a(n) = Sum_{k=0..n} 2^(n-k) * binomial(3*n+2,k) * binomial(3*n-k-1,n-k).
A386866
a(n) = Sum_{k=0..n} 2^(n-k) * binomial(3*n+2,k) * binomial(3*n-k-1,n-k).
Terms
- a(0) =1a(1) =9a(2) =132a(3) =2197a(4) =38649a(5) =701292a(6) =12979360a(7) =243541725a(8) =4616122851a(9) =88173726337
External references
- oeis: A386866