A discrete version of the Mangoldt function: if n is prime then ceiling(log(n)) else 0.

Terms

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