OFFSET
1,2
COMMENTS
Theorem: If both numbers q and 2q-1 are primes and m=q*(2q-1) then 8^m==8 (mod m) (m is in the sequence) iff q is of the form 4k+1. 2701,18721,49141,104653,226801,665281,721801,... are such terms.
MAPLE
q:= m-> not isprime(m) and 8&^m mod m = 8 mod m:
select(q, [$1..5000])[]; # Alois P. Heinz, Apr 19 2022
MATHEMATICA
Select[Range[6000], ! PrimeQ[ # ] && Mod[8^#, # ] == Mod[8, # ] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Farideh Firoozbakht, Sep 12 2006
EXTENSIONS
Missing a(8)-a(18) inserted by Georg Fischer, Apr 19 2022
STATUS
approved