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A088605
a(n) is the beginning of the first set of n consecutive primes such that the concatenation of n with each of these primes is also prime.
0
3, 23, 7, 720901, 956759, 41, 4769888443
OFFSET
1,1
COMMENTS
a(8) > 10^11, a(9) = 11408039. - Hans Havermann, Sep 16 2005
EXAMPLE
a(3) = 7 because 7, 11 and 13 are 3 consecutive primes and 37, 311 and 313 are all prime.
MATHEMATICA
<<NumberTheory`; Do[s = 0; l = {}; While[Length[l] < n, s++; l = List[Prime[s]]; k = 1; While[k < n, p = l[[k]]; AppendTo[l, NextPrime[p]]; k++ ]; l = ToString /@ l; l = Map[ToString[n] <> #&, l]; l = ToExpression /@ l; l = Select[l, PrimeQ]]; Print[Prime[s]], {n, 1, 30}]; (* Ryan Propper, Aug 14 2005 *)
CROSSREFS
Sequence in context: A196083 A375650 A285098 * A272816 A063562 A130475
KEYWORD
base,hard,nonn
AUTHOR
Amarnath Murthy, Oct 15 2003
EXTENSIONS
Corrected, extended and edited by Ryan Propper and David Wasserman, Aug 14 2005
a(7) from Hans Havermann, Sep 16 2005
STATUS
approved