a(n) = Sum_{i,j = 0..n} C(n, i)^2*C(n, j)^2*C(i+j, i)*2^(i+j).
A383274
a(n) = Sum_{i,j = 0..n} C(n, i)^2*C(n, j)^2*C(i+j, i)*2^(i+j).
Terms
- a(0) =1a(1) =13a(2) =441a(3) =20629a(4) =1119361a(5) =66116013a(6) =4126228569a(7) =267666251733
External references
- oeis: A383274