a(n) = phi(Sum_{i=1..n} prime(i)).

Terms

a(0) =1a(1) =4a(2) =4a(3) =16a(4) =12a(5) =40a(6) =28a(7) =60a(8) =40a(9) =84a(10) =64a(11) =196a(12) =96a(13) =280a(14) =160a(15) =252a(16) =160a(17) =332a(18) =280a(19) =420a(20) =352a(21) =672a(22) =396a(23) =636a(24) =416a(25) =756a(26) =624a(27) =912a(28) =576a(29) =1044