A242619 a(n) is the smallest number in the interval (1, 2^(2^(n-1))) that is a member of a pair of integers the sum of whose squares is equal to the Fermat number 2^(2^n) + 1, or 0 if no such number exists.

0, 0, 0, 0, 0, 20449, 1438793759, 8479443857936402504, 17340632172455487023654788790090010704

Offset

0,6

Comments

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

Links

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

Wikipedia, Fermat number

Crossrefs

Cf. A000215, A242620.

Sequence in context: A223466 A281658 A234304 * A224619 A186060 A253866

Adjacent sequences: A242616 A242617 A242618 * A242620 A242621 A242622

Keyword

nonn

Author

Arkadiusz Wesolowski, May 19 2014

Status

approved