Partial sums of primes, if 1 is regarded as a prime (as it was until quite recently, see A008578).

Terms

a(0) =1a(1) =3a(2) =6a(3) =11a(4) =18a(5) =29a(6) =42a(7) =59a(8) =78a(9) =101a(10) =130a(11) =161a(12) =198a(13) =239a(14) =282a(15) =329a(16) =382a(17) =441a(18) =502a(19) =569a(20) =640a(21) =713a(22) =792a(23) =875a(24) =964a(25) =1061a(26) =1162a(27) =1265a(28) =1372a(29) =1481