a(n) = (n!)^2 * Sum_{k=0..n} 3^(n-k) / (k!)^2.
A336805
a(n) = (n!)^2 * Sum_{k=0..n} 3^(n-k) / (k!)^2.
Terms
- a(0) =1a(1) =4a(2) =49a(3) =1324a(4) =63553a(5) =4766476a(6) =514779409a(7) =75672573124
External references
- oeis: A336805
A336805
a(n) = (n!)^2 * Sum_{k=0..n} 3^(n-k) / (k!)^2.