Right-hand diagonal of A035309.

Terms

a(0) =1a(1) =1a(2) =1a(3) =10a(4) =21a(5) =483a(6) =1485a(7) =56628a(8) =225225a(9) =12317877a(10) =59520825a(11) =4304016990a(12) =24325703325