a(n) = 1 + Sum_{i=2..n-1} n*a(i).

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =21a(5) =131a(6) =943a(7) =7701a(8) =70409a(9) =712891a(10) =7921011a(11) =95844233a(12) =1254688141a(13) =17670191319a(14) =266412115271