[seqfan] Two neighboring digits sum up to a prime

[Eric Angelini]

Hello SeqFans,
this should be easy to extend:

Smallest integer not yet in S such that two neighboring 
digits of S sum up to a prime:

S = 1,2,3,4,7,6,5,8,9,20,21,11,12,16,50,23,25,29,41,43,47,49,...
Best,
É.