a(n) = Sum_{d|n} (n/d)^(d-1).

Terms

a(0) =1a(1) =2a(2) =2a(3) =4a(4) =2a(5) =9a(6) =2a(7) =14a(8) =11a(9) =23a(10) =2a(11) =83a(12) =2a(13) =73a(14) =108a(15) =202a(16) =2a(17) =546a(18) =2a(19) =905a(20) =780a(21) =1037a(22) =2a(23) =5553a(24) =627a(25) =4111a(26) =6644a(27) =12647a(28) =2a(29) =40605