OFFSET
1,1
COMMENTS
A very interesting observation due to Peter Bala: about half of the terms from the sequence have the form p*(4*p - 3), where p is prime. For this form of Fermat pseudoprimes see the sequences A213812 and A215343.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Poulet Number
PROG
(PARI) list(lim)=my(v=List(), t); forprime(p=3, sqrtint(lim\=1), forprime(q=p+2, lim\p, t=p*q; if(t%10==7 && Mod(2, t)^t==2, listput(v, t)))); Set(v) \\ Charles R Greathouse IV, Jun 30 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Marius Coman, Sep 13 2012
STATUS
approved