[seqfan] Prime by concatenation

[Eric Angelini]

Hello Seqfans,
Concatenate any two digits of S separated by a comma: 
the resulting 2-digit number is prime.

If we accept that [70,2] produces the prime "2"
(concatenation of 0 and 2), then S is a permutation
of {the positive integers} - {4,6,8,9}:

S = 1,3,7,9,70,2,30,5,31,10,20,21,11,12,32,33,13,14,15,...

As usual, S was extended with the smallest integer
not yet present in S and not leading to a contradiction.

Best,
É.