3,2
a(2) = 131072, or it is a Sierpiński number multiplied by a power of 2.
Because a(1) = 8 but a(2) is unknown, we do not include it here; we set the offset to 3.
a(2) <= 201446503145165177.
Table of n, a(n) for n=3..11.
Dan Krywaruczenko, A Reverse Sierpiński Number Problem
Cf. A123159.
Sequence in context: A013800 A013870 A195898 * A164526 A278897 A123652
Adjacent sequences: A263497 A263498 A263499 * A263501 A263502 A263503
nonn,more,hard
Arkadiusz Wesolowski, Oct 19 2015
approved
