a(1) = 1, for n > 1: a(n) = phi(sum of the previous terms) where phi is Euler's totient function.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =6a(6) =8a(7) =22a(8) =24a(9) =44a(10) =112a(11) =120a(12) =176a(13) =520a(14) =692a(15) =1732a(16) =1440a(17) =2592a(18) =4032a(19) =6480a(20) =11088a(21) =18720a(22) =23760a(23) =43200a(24) =69984a(25) =123120a(26) =174960a(27) =321732a(28) =408240a(29) =641520