Fifth-from-right diagonal of triangle A121207.

Terms

a(0) =1a(1) =1a(2) =6a(3) =27a(4) =125a(5) =635a(6) =3488a(7) =20425a(8) =126817a(9) =831915a(10) =5744784a(11) =41618459a(12) =315388311a(13) =2493721645a(14) =20526285716a(15) =175529425815