a(n) = (5^n/n!^2) * Product_{k=0..n-1} (10k+1)*(10k+4).
A184891
a(n) = (5^n/n!^2) * Product_{k=0..n-1} (10k+1)*(10k+4).
Terms
- a(0) =1a(1) =20a(2) =3850a(3) =1078000a(4) =355066250a(5) =128107903000
External references
- oeis: A184891
A184891
a(n) = (5^n/n!^2) * Product_{k=0..n-1} (10k+1)*(10k+4).