
COMMENTS

This sequence is related to the remarkable occurrence of primes in the sequence 109, 10099, 1000999, etc. Credit for second and third terms goes to Jens Kruse Andersen.
Once a 5th term, a(8), is available, this sequence will be essentially complete: a(9)=66 and a(k)=2 for k>9 with near certainty (known true for several terms, and the contrary at any later point would comparable to a return to the origin of a random walk on the line that is biased in one direction and already many 'paces' along in that direction).
