a(n) = A083385(n)/n.

Terms

a(0) =1a(1) =4a(2) =22a(3) =154a(4) =1306a(5) =12994a(6) =148282a(7) =1908274a(8) =27333706a(9) =431220034a(10) =7428550042a(11) =138737478994