a(1)=1, a(n+1) = a(n) + spf(Sum_{i=1..n} a(i)), where spf=A020639 (smallest prime factor).

Terms

a(0) =1a(1) =2a(2) =5a(3) =7a(4) =10a(5) =15a(6) =17a(7) =20a(8) =27a(9) =29a(10) =36a(11) =49a(12) =51a(13) =320a(14) =339a(15) =341a(16) =344a(17) =1957a(18) =1959a(19) =1962a(20) =1965a(21) =1967a(22) =13390a(23) =13393a(24) =13395a(25) =13406a(26) =13409a(27) =13411a(28) =13414a(29) =13433