A144742 Integers m such that phi(2, m) = A144740(m) > phi(2, k) for 0 < k < m.

5, 7, 11, 17, 23, 29, 37, 41, 47, 53, 59, 67, 71, 79, 83, 89, 97, 107, 113, 127, 131, 137, 149, 157, 163, 167, 173, 179, 191, 197, 211, 223, 227, 239, 251, 257, 263, 269, 277, 281, 293, 307, 311, 317, 331, 337, 347, 359, 367, 373, 379, 383, 389, 397, 401, 409

Offset: 1

Author

Reikku Kulon, Sep 20 2008

Keywords

• easy
• nonn

Comments

Subset of the primes (A000040).

Except for 5 and 7, if one member of a twin prime pair is included, the other is not.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A001097, A144740.

A005385 is a subsequence.

Programs

Mathematica

phi2[n_] := phi2[n] = Count[Range[n-1], _?(Total[Last /@ FactorInteger[#]] == 2 && CoprimeQ[#, n] &)];
Select[Range[300], And @@ Table[phi2[#] > phi2[k], {k, #-1}] &]
(* Andrey Zabolotskiy, Sep 09 2019 *)