OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
If k=24, then k77777 = 2477777 (prime).
If k=66, then k77777 = 6677777 (prime).
If k=99, then k77777 = 9977777 (prime).
MATHEMATICA
Select[Range[500], PrimeQ[#*10^5+77777]&] (* Harvey P. Dale, Sep 19 2020 *)
PROG
(Magma) [ n: n in [1..700] | IsPrime(Seqint([7, 7, 7, 7, 7] cat Intseq(n))) ]; // Vincenzo Librandi, Feb 04 2011
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Parthasarathy Nambi, Feb 22 2005
STATUS
approved