A274915 Powers of odd non-Fermat primes.

1, 7, 11, 13, 19, 23, 29, 31, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 121, 127, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 263, 269, 271, 277, 281, 283, 293, 307, 311

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 11 2016

Keywords

• nonn
• easy

Comments

n is in the sequence if n = p^m where p is in A138889 and m >= 0. - Robert Israel, Sep 15 2017

The difference between two divisors of n is never a power of 2. The first number with this property that is not in the sequence is 91. - Robert Israel, Sep 15 2017

Subsequence of A061345.

Examples

			49 is in this sequence because 49 = 7^2 and 7 is not a Fermat prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A019434, A061345, A092506, A138889, A277994.

Programs

Maple

N:= 500: # to get all terms <= N
P:= select(isprime, {seq(i,i=7..N,2)}) minus {seq(2^i+1, i=1..ilog2(N))}:
sort(convert(map(p -> seq(p^k,k=0..floor(log[p](N))), P), list)); # Robert Israel, Sep 15 2017

Formula

A277994(a(n)) = 0.

Extensions

Edited, new name, and corrected by Robert Israel, Sep 15 2017