a(n) = Sum_{d | n} mu(n/d) * Bell(d-1).

Terms

a(0) =1a(1) =0a(2) =1a(3) =4a(4) =14a(5) =50a(6) =202a(7) =872a(8) =4138a(9) =21132a(10) =115974a(11) =678514a(12) =4213596a(13) =27644234a(14) =190899306a(15) =1382957668a(16) =10480142146a(17) =82864865614a(18) =682076806158