A309191 - OEIS

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.

2, 2, 31, 4603, 910307, 352367441, 23908162969, 483148266971

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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: A276821 A267726 A371562 * A372305 A353911 A303568

Adjacent sequences: A309188 A309189 A309190 * A309192 A309193 A309194

KEYWORD

nonn,base,more

AUTHOR

Jean-Marc Rebert, Jul 16 2019

STATUS

approved