

A309191


a(n) is the least prime such that each concatenation of 1 <= k <= n consecutive primes beginning with a(n) is prime, or 0 if no such prime exists.


1




OFFSET

1,1


LINKS

Table of n, a(n) for n=1..8.
Carlos Rivera, Puzzle 708 Find sets of k consecutive primes such that ..., The Prime Puzzles & Problems Connection.


EXAMPLE

a(2)=2; 2, 3 are 2 consecutive primes and their concatenation 23 is also prime.
a(3)=31 since 31, 37, and 41 are 3 consecutive primes and 3137 and 313741 are both prime.


MATHEMATICA

a[n_] := Block[{p = Prime@ Range@ n}, While[! AllTrue[Range[2, n], PrimeQ@ FromDigits@ Flatten@ IntegerDigits@ Take[p, #] &], p = Append[ Rest@ p, NextPrime@ Last@ p]]; p[[1]]]; Array[a, 5] (* Giovanni Resta, Jul 16 2019 *)


CROSSREFS

Cf. A030996.
Sequence in context: A343172 A276821 A267726 * A303568 A121788 A018976
Adjacent sequences: A309188 A309189 A309190 * A309192 A309193 A309194


KEYWORD

nonn,base,more


AUTHOR

JeanMarc Rebert, Jul 16 2019


STATUS

approved



