Number of distinct primes dividing p+1 as p runs through the primes.

Terms

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