Sum of exponents in prime-power factorization of n-th prime - 1.

Terms

a(0) =0a(1) =1a(2) =2a(3) =2a(4) =2a(5) =3a(6) =4a(7) =3a(8) =2a(9) =3a(10) =3a(11) =4a(12) =4a(13) =3a(14) =2a(15) =3a(16) =2a(17) =4a(18) =3a(19) =3a(20) =5a(21) =3a(22) =2a(23) =4a(24) =6a(25) =4a(26) =3a(27) =2a(28) =5a(29) =5