a(n) = Sum_{k=0..n} (2*k-1)!!*binomial(2*n-k, n).
A293469
a(n) = Sum_{k=0..n} (2*k-1)!!*binomial(2*n-k, n).
Terms
- a(0) =1a(1) =3a(2) =12a(3) =57a(4) =330a(5) =2436a(6) =23226a(7) =277389a(8) =3966534a(9) =65517210a(10) =1220999208a(11) =25279328958a(12) =575024187192
External references
- oeis: A293469