Definition:Fermat Pseudoprime/Base 4/Sequence

Sequence of Fermat Pseudoprimes to Base $4$
The sequence of Fermat pseudoprimes base $4$ begins:
 * $15, 85, 91, 341, 435, 451, 561, 645, 703, 1105, 1247, 1271, 1387, 1581, 1695, 1729, 1891, 1905, 2047, 2071, 2465, \ldots$