% Generate the first N elements of the Van Eck sequence
eck = proc (n: int) returns (array[int])
    ai = array[int]
    e: ai := ai$fill(0, n, 0)

    for i: int in int$from_to(ai$low(e), ai$high(e)-1) do
        for j: int in int$from_to_by(i-1, ai$low(e), -1) do
            if e[i] = e[j] then
                e[i+1] := i-j
                break
            end
        end
    end
    return(e)
end eck

% Show 0..9 and 990..999
start_up = proc ()
    po: stream := stream$primary_output()
    e: array[int] := eck(1000)

    stream$puts(po, "  0 -   9: ")
    for i: int in int$from_to(0,9) do
        stream$putright(po, int$unparse(e[i]), 4)
    end
    stream$puts(po, "\n990 - 999: ")
    for i: int in int$from_to(990,999) do
        stream$putright(po, int$unparse(e[i]), 4)
    end
    stream$putl(po, "")
end start_up