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A159031
Primes of the form "1 [0]_n 7" - with zeros between 1 and 7.
12
17, 107, 10007, 100000007, 1000000007, 1000000000000000000000007, 1000000000000000000000000000000000000000000000000000000000007
OFFSET
1,1
COMMENTS
The next term, a(8), has 111 digits. - Harvey P. Dale, Nov 12 2011
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
Cf. A088274. - Robert G. Wilson v, Apr 05 2009
Sequence in context: A007682 A125327 A126485 * A080441 A135400 A372583
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Apr 02 2009
EXTENSIONS
a(7) from Robert G. Wilson v, Apr 05 2009
STATUS
approved