Building on this question, what is the most efficient counting function for distinct prime factors? It would obviously be more efficient if Prime
and PrimePi
were used instead of PrimeNu
, as ybeltukov and Coolwater used in their brilliant solutions to the PrimeOmega
counting function question. I was wondering whether there was any way to do something similar in this instance?
The best I have so far is a (very) minor modification of ubpdqn's reply to my previous question:
cnt[k_, n_] := Last@Reap[Sow[1, PrimeNu@#] & /@ Range[n], k, Total@#2 &]