I have changed my program searching for AP with difference 19# from
AP19 exhaustive to AP21 exhaustive, which allowed me to move much
faster.

I have found:

AP21: 28112131522731197609+19#*n, n=0..20

This is:
The smallest EXISTING AP21 with difference 19#.
The first KNOWN case of 21 simultaneous primes according to JKA rules.
The first KNOWN AP21 with any difference and terms above 2^64.

I have used 42 computers yesterday during the day and total of 58
overnight, making something like 50 computers on average times 24
hours since the program was restarted after change.

After the restart I found one AP19, and the above AP21 was the second AP19+.

With 5 AP18 (for a total of 7 AP18+) I think I fully deserved to find
one AP19, perhaps two with some luck. I shouldn't really expect any
AP20, so AP21 is a miracle.

Jarek