Here is a new AP15 record at 54 digits:-

(237375311+118560155*n)*109#+1 is prime for n=0..14

All confirmed prime with PFGW -tc

Input/output statistics:-

Numbers tested by NewPGen: 2*10^9

NewPGen reduced these (by sieving to 50 billion) to: 3.94*10^8

PRP's found by PFGW: 140,719,122

AP14's found: 4

AP15's found: 1

Run-time statistics:-

NewPGen: 2 GHz-hrs

PFGW: 3 GHz-days

Pascal program to find AP's: 106 GHz-days

The AP15 came after only 4 AP14's had been found, which was about 4 times sooner than anticipated.

Note that, as n increases, the effort required to find the millions of PRPs is dwarfed by that needed to find a single APn.

Even for n as small as 15, the former is typically about 1% of the latter.

-Mike Oakes