OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
613 is a term because it is a prime obtained by prefixing a 6 to the prime 13.
6101 is a term because it is a prime obtained by prefixing a 6 to the prime 101.
MAPLE
p:= 0: A:= NULL:
while p < 1000 do
p:= nextprime(p);
q:= 10^(ilog10(p)+1)*6+p;
if isprime(q) then A:= A, q; fi
od:
A; # Robert Israel, Jul 17 2017
MATHEMATICA
Select[Table[FromDigits[Join[IntegerDigits[6], IntegerDigits[Prime[n]]]], {n, 110}], PrimeQ]
Select[6*10^IntegerLength[#]+#&/@Prime[Range[150]], PrimeQ] (* Harvey P. Dale, Apr 03 2022 *)
PROG
(Magma) [k: p in PrimesUpTo(800) | IsPrime(k) where k is Seqint(Intseq(p) cat [6])];
(PARI) terms(n) = my(i=0); forprime(p=1, , my(s=eval(Str(6, p))); if(ispseudoprime(s), print1(s, ", "); i++); if(i==n, break))
/* Print initial 50 terms as follows */
terms(50) \\ Felix Fröhlich, Jul 15 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Vincenzo Librandi, Jul 15 2017
STATUS
approved