# 1000, 1000+n, ..., 10000-n
# ? n
Seq ← (
  # ⍤"illegal argument"⊸∊⇡₁8999
  ⌈⊸˜÷9000 ⊙1000
  ⍥⟜⊸+ # ? 9000÷n n 1000 
)
Prime ← =1/+≠1°/×

⇡₁8999
⟜⍚Seq
⍚⇡
⍚⊞+
/◇⊂⍚♭
⊏⊸(Prime
   \(×⤙+)
   ⊚=3
   ˜⊞+⇌¯⇡3)
≡₀◇⍆°⋕
⊸≡₂(↧∩⌞≍°⊟₃)
⊡⊢⊚
/⊂