P ← =1/+≠1°/×
C ← ↧∩(/↧P)⊸⍜°⋕(/⍚⊂⍉⧅≠2)
# [primes less than n] ? n
Primes ← ⍥(⊂2)>2⟜(▽⊸P+1⍜÷(⇡⌊)2)
Primes700
▽wait⊸≡poolC⧅>4