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.

3, 23, 7, 720901, 956759, 41, 4769888443

Offset

1,1

Comments

a(8) > 10^11, a(9) = 11408039. - Hans Havermann, Sep 16 2005

Links

Table of n, a(n) for n=1..7.

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

Adjacent sequences: A088602 A088603 A088604 * A088606 A088607 A088608

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