OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..2500
EXAMPLE
7 is in the sequence because 1117 is prime.
73 is in the sequence because 11173 is prime.
103 is in the sequence because 111103 is prime.
MAPLE
a:= proc(n) local k; for k from 1 +`if`(n=1, 0, a(n-1))
while not isprime(parse(""||111||k)) do od; a(n):=k
end:
seq(a(n), n=1..100); # Alois P. Heinz, Jul 30 2014
MATHEMATICA
Select[Range[1000], PrimeQ[FromDigits[Join[{1, 1, 1}, IntegerDigits[ # ]]]] &] (* _Alonso Delarte_, Sep 06 2005 *)
Select[Range[600], PrimeQ[111 10^IntegerLength[#] + #] &] (* Vincenzo Librandi, Jul 30 2014 *)
PROG
(Magma) [ n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [1, 1, 1])) ];
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Sep 04 2005
EXTENSIONS
More terms from Alonso del Arte, Sep 06 2005
STATUS
approved