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

Terms

a(0) =1a(1) =4a(2) =5a(3) =17a(4) =7a(5) =56a(6) =9a(7) =146a(8) =78a(9) =298a(10) =13a(11) =1501a(12) =15a(13) =2276a(14) =1265a(15) =9219a(16) =19a(17) =25716a(18) =21a(19) =77519a(20) =16929a(21) =177328a(22) =25a(23) =739582a(24) =7808a(25) =1594562a(26) =264382a(27) =5611241a(28) =31a(29) =15699452