A067932 Primes p such that p+3 == 0 (mod phi(p+3)).

3, 5, 13, 29, 61, 509, 1021, 4093, 16381, 1048573, 4194301, 16777213, 536870909, 19807040628566084398385987581, 83076749736557242056487941267521533, 5316911983139663491615228241121378301

Offset: 1

Author

Benoit Cloitre, Feb 22 2002

Keywords

• easy
• nonn

Comments

phi(n) divides n iff n=1 or n=2^w*3^u for w>=1 and u>=0 (see A007694). Such an n can only have the form p+3 if n=6 or n is a power of 2. So the terms of the sequence are 3 and the primes of the form 2^n-3, listed in A050415.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..30

Programs

Mathematica

Prepend[Select[2^Range[2, 200]-3, PrimeQ], 3]

Extensions

Edited and extended by Robert G. Wilson v, Feb 27 2002 and by Dean Hickerson, Mar 21 2002