# Generate Van Eck sequence.
F ← (
  ◡<⊙⊙◌⊃(⋅⧻|⊸˜⨂)°⊂. # Check where/if first digit already appeared.
  ⊂⨬(⋅⋅0|⋅+₁)       # If new, prepend zero, else last index it was in.
)
⇌⍥F999 [0]      # Generate 1000 terms and reverse.
⊃(&p↙¯)(&p↙∘)10 # Print first and last 10 terms.