A281623 Numbers of the form 2^phi(m) + 1, where phi = A000010 = Euler totient function.

3, 5, 17, 65, 257, 1025, 4097, 65537, 262145, 1048577, 4194305, 16777217, 268435457, 1073741825, 4294967297, 68719476737, 1099511627777, 4398046511105, 17592186044417, 70368744177665, 281474976710657, 4503599627370497, 18014398509481985, 72057594037927937

Offset

1,1

Comments

Possible values of A243305 (2^phi(n) + 1).

The first 5 known Fermat primes from A019434 are in the sequence.

Links

Table of n, a(n) for n=1..24.

Example

5 = 2^2 + 1 is a term because there are 3 numbers n (3, 4 and 6) with phi(n) = 2.

Mathematica

Union[2^EulerPhi@ Range[10^3] + 1] (* Michael De Vlieger, Jan 30 2017 *)

Prog

(Magma) Set(Sort([2^(EulerPhi(n)) + 1: n in[1..500]]))

Crossrefs

Cf. A000010, A019434, A243305.

Sequence in context: A219108 A176964 A085749 * A350142 A278741 A265425

Adjacent sequences: A281620 A281621 A281622 * A281624 A281625 A281626

Keyword

nonn

Author

Jaroslav Krizek, Jan 25 2017

Status

approved