E.g.f.: Sum_{n>=0} ( Sum_{k=1..n} x^k/k )^n / n!.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =10a(5) =46a(6) =236a(7) =1422a(8) =8856a(9) =68868a(10) =592164a(11) =5421384a(12) =54606168a(13) =599176800a(14) =7035165528a(15) =89675702976