Dear Neil and Seqfans, May I put this comment on A000040 ? %I A000040 %C A000040 There is a unique decomposition of the primes: provided the weight A117078(n) is > 0, we have prime(n) = weight * level + gap, or A000040(n) = A117078(n) * A117563(n) + A001223(n). %A A000040 Remi Eismann (reismann at free.fr), Feb 16 2007 Best Rémi