OFFSET
1,1
COMMENTS
The corresponding larger counterparts are 4371, 13747, 31621, 6973063, 208969223.
The corresponding gaps between the consecutive pseudoprimes are 2, 6, 12, 6, 22.
a(6) > 10^15, if it exists.
EXAMPLE
4369 is a term since it is a Fermat pseudoprime to base 2, and between it and the next Fermat pseudoprime to base 2, 4371, there is only one number, 4370, which is composite.
MATHEMATICA
psp = Cases[Import["https://oeis.org/A001567/b001567.txt", "Table"], {_, _}][[;; , 2]]; s = {}; Do[If[NextPrime[psp[[k]]] > psp[[k + 1]], AppendTo[s, psp[[k]]]], {k, 1, Length[psp] - 1}]; s
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Amiram Eldar, Jun 01 2020
STATUS
approved