[seqfan] "Stubborn primes"

[Vladimir Shevelev]

Dear SeqFans,

On a rest I experimented with consecutive primes >=5, concatunating to every
of them 3,33,333,.... and catched a moment when there arises a new prime.
As a rule,  I rather fast obtained a prime. The first difficulty arises with 13.
Only number 1333333333333333 was prime. So I call 13 a "stuborn prime". After
that with help Peter I have submitted to-day  sequence A232210. The calculated records of numbers of concatunating 3's are 1,14,23,50,252,4752 with the
correspoding primes 5,13,131,653, 883,1279,... Beginning with the second prime,
I call them "stubborn".
I wonder are they already considered and what is a continuation of sequence of stubborn primes?

Have a good day,
Vladimir