A166257 Odd numbers not of the form prime(k) + phi(prime(k)).

1, 7, 11, 15, 17, 19, 23, 27, 29, 31, 35, 39, 41, 43, 47, 49, 51, 53, 55, 59, 63, 65, 67, 69, 71, 75, 77, 79, 83, 87, 89, 91, 95, 97, 99, 101, 103, 107, 109, 111, 113, 115, 119, 123, 125, 127, 129, 131, 135, 137, 139, 143, 147, 149, 151, 153, 155, 159, 161, 163, 167

Offset: 1

Author

Juri-Stepan Gerasimov, Oct 10 2009

Keywords

• nonn
• easy

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000010, A000040, A005408.

Programs

Maple

L := 100; S := {}:
for i from 2 to L do
  for j from 2 to L do
    if i*j <= L then S := `union`(S, {2*i*j-1}) end if;
  end do;
end do:
{1} union S; # Peter Bala, Jan 30 2025

Mathematica

Module[{upto=200},Complement[Range[1,upto,2],Table[n+EulerPhi[n],{n,Prime[ Range[PrimePi[upto]]]}]]] (* Harvey P. Dale, Jun 21 2019 *)

Formula

{1} U {A005408 \ A076274 }. - R. J. Mathar, May 21 2010

Extensions

Entries checked by R. J. Mathar, May 21 2010.