a(1)=1, a(2)=2; thereafter a(n) = (1/n!)*Sum_{i=0..floor(n/2)} 4*(2*n+1)!*(2*n-i-4)!/(i!*(n-i-2)!*(2*n-i+1)).
A329775
a(1)=1, a(2)=2; thereafter a(n) = (1/n!)*Sum_{i=0..floor(n/2)} 4*(2*n+1)!*(2*n-i-4)!/(i!*(n-i-2)!*(2*n-i+1)).
Terms
- a(0) =1a(1) =2a(2) =1520a(3) =134640a(4) =24272640a(5) =7527582720
External references
- oeis: A329775