A107800 a(n) = number of distinct primes dividing A006049(n) (and dividing A006049(n)+1).

1, 1, 1, 1, 1, 2, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2

Offset: 1

Author

Leroy Quet, Mar 24 2007

Keywords

• nonn

Comments

a(n) first equals 3 when n is such that A006049(n) = 230.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..2500 from T. D. Noe)

Crossrefs

Cf. A001221, A006049, A052215.

Programs

Mathematica

f[n_] := Length@FactorInteger[n];t = f /@ Range[300];f /@ Flatten@Position[Rest[t] - Most[t], 0] (* Ray Chandler, Mar 27 2007 *)

Formula

a(n) = A001221(A006049(n)).

Extensions

Extended by Ray Chandler, Mar 27 2007