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

1,2

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.

Links

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

Formula

A277994(a(n)) = 0.

Example

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

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

Crossrefs

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

Sequence in context: A092246 A084468 A292315 * A336381 A152469 A115558

Adjacent sequences: A274912 A274913 A274914 * A274916 A274917 A274918

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Nov 11 2016

Extensions

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

Status

approved