I was trying to get AP17 with difference 107*61#. The reason why I
didn't use primorial difference is that I needed 9 primes coprime with
the sequence difference and with product below (2^62)/15 and primes 67-103
are the largest 9 consecutive primes with that property, so I had to
avoid them as factors of the sequence difference.

I was rather unlucky sitting there with 10 AP15's and nothing longer than
that (I should have AP16 every 4-5 AP15's).

And right now came the first sequence longer than 15 terms:

62749659973280668140514103 + 107*61#*n, n=0..18

I was expecting to get AP17. I was taking into acount small chance of AP18.
But I was never thinking of AP19 of that size, so I was really surprised
when it has appeared.

Jarek