OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..2000
EXAMPLE
If n=3 then 77n = 773 (prime).
If n=93 then 77n = 7793 (prime).
MAPLE
select(n -> isprime(77*10^(1+ilog10(n))+n), [$1..1000]); # Robert Israel, Jul 30 2014
MATHEMATICA
Select[Range[700], PrimeQ[77 10^IntegerLength[#] + #] &] (* Vincenzo Librandi, Jul 30 2014 *)
PROG
(Magma) [n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [7, 7])) ]; // Vincenzo Librandi, Jul 30 2014
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Sep 01 2005
EXTENSIONS
More terms from Vincenzo Librandi, Mar 27 2010
STATUS
approved