OFFSET
1,1
COMMENTS
The next term, a(8), has 111 digits. - Harvey P. Dale, Nov 12 2011
LINKS
Dario Alejandro Alpern, Factorization using the Elliptic Curve Method.
Makoto Kamada, Prime numbers of the form 100...007.
EXAMPLE
1000000000000000000000007 is a prime with 23 zeros between 1 and 7.
MATHEMATICA
Do[ If[ PrimeQ[10^n + 7], Print[10^n + 7]], {n, 100}] (* Robert G. Wilson v, Apr 05 2009 *)
Select[Table[FromDigits[Join[{1}, PadRight[{}, n, 0], {7}]], {n, 0, 120}], PrimeQ] (* Harvey P. Dale, Nov 12 2011 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Apr 02 2009
EXTENSIONS
a(7) from Robert G. Wilson v, Apr 05 2009
STATUS
approved