OFFSET
1,1
COMMENTS
Primes of the form (2*10^k + 1)/3. - Vincenzo Librandi, Nov 16 2010
Occur in the factorization of some of the numbers of the form 13...3 not in A093671, cf. second Kamada link. - M. F. Hasler, Sep 14 2014
LINKS
Makoto Kamada, Prime numbers of the form 66...667.
Makoto Kamada, Factorizations of 133...33.
MAPLE
A093170:=n->`if`(isprime((2*10^n+1)/3), (2*10^n+1)/3, NULL): seq(A093170(n), n=1..70); # Wesley Ivan Hurt, Sep 14 2014
MATHEMATICA
Select[Table[FromDigits[PadLeft[{7}, n, 6]], {n, 70}], PrimeQ] (* Harvey P. Dale, Jan 26 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Rick L. Shepherd, Mar 26 2004
EXTENSIONS
Edited by Ray Chandler, Feb 23 2012
STATUS
approved