a(1)=1, a(2) = 2. a(n) = a(n-2) + (largest prime dividing a(n-1)).

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =8a(5) =7a(6) =15a(7) =12a(8) =18a(9) =15a(10) =23a(11) =38a(12) =42a(13) =45a(14) =47a(15) =92a(16) =70a(17) =99a(18) =81a(19) =102a(20) =98a(21) =109a(22) =207a(23) =132a(24) =218a(25) =241a(26) =459a(27) =258a(28) =502a(29) =509