a(n) = sum of exponents in prime-power factorization of 2*prime(n)-1.

Terms

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