OFFSET
1,1
COMMENTS
All terms == 5 (mod 6).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
367733 is in the sequence because 367, 2*367-1=733, and 367733 are all primes.
MAPLE
f:= proc(p) local q, r;
if not isprime(p) then return NULL fi;
q:= 2*p-1;
r:= p*10^(1+ilog10(q))+q;
if isprime(r) and isprime(q) then r else NULL fi;
end proc:
map(f, [2, seq(i, i=7..20000, 6)]);
PROG
(PARI) forprime(p=1, 1e4, my(cc=eval(concat(Str(p), Str(2*p-1)))); if(ispseudoprime(2*p-1) && ispseudoprime(cc), print1(cc, ", "))) \\ Felix Fröhlich, Jan 09 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
J. M. Bergot and Robert Israel, Jan 09 2019
STATUS
approved