F van_eck(c)
   [Int] r
   V n = 0
   V seen = [0]
   V val = 0
   L
      r.append(val)
      I r.len == c
         R r
      I val C seen[1..]
         val = seen.index(val, 1)
      E
         val = 0
      seen.insert(0, val)
      n++

print(‘Van Eck: first 10 terms:   ’van_eck(10))
print(‘Van Eck: terms 991 - 1000: ’van_eck(1000)[(len)-10..])