OFFSET
1,1
COMMENTS
The semiprimes of this form are 5183, 38879, 279935, 1959551, 90699263, 604661759, 3990767615, 26121388031, 169789022207, 1097098297343, ...
a(32) >= 423. - Tyler Busby, Mar 19 2023
LINKS
factordb.com, Status of 423*6^423-1.
MATHEMATICA
Select[Range[352], PrimeOmega[# 6^# - 1]==2&]
PROG
(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [n: n in [2..352] | IsSemiprime(s) where s is n*6^n-1];
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, May 12 2014
EXTENSIONS
a(26)-a(31) from Carl Schildkraut, Aug 17 2015
STATUS
approved