0,6

2^(2^n) + 1 belongs to A019434 if and only if a(n) = 0.

Table of n, a(n) for n=0..8.

Wikipedia, Fermat number

Cf. A000215, A242619.

Sequence in context: A093791 A083488 A181114 * A203046 A180163 A180202

Adjacent sequences: A242617 A242618 A242619 * A242621 A242622 A242623

nonn

Arkadiusz Wesolowski, May 19 2014

approved