OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
If k=13, then k7777777 = 137777777 (prime).
If k=57, then k7777777 = 577777777 (prime).
If k=96, then k7777777 = 967777777 (prime).
MATHEMATICA
Select[Range[600], PrimeQ[#*10^7+7777777]&] (* Harvey P. Dale, Jan 02 2015 *)
PROG
(Magma) [ n: n in [1..700] | IsPrime(Seqint([7, 7, 7, 7, 7, 7, 7] cat Intseq(n))) ]; // Vincenzo Librandi, Feb 03 2011
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Parthasarathy Nambi, Feb 25 2005
STATUS
approved