sequence sb = {1,1}
integer c = 2

function stern_brocot(integer n)
    while length(sb)<n do
        sb &= sb[c]+sb[c-1] & sb[c]
        c += 1
    end while
    return sb[1..n]
end function

sequence s = stern_brocot(15)
puts(1,"first 15:")
?s
integer n = 16, k
sequence idx = tagset(10)
for i=1 to length(idx) do
    while 1 do
        k = find(idx[i],s)
        if k!=0 then exit end if
        n *= 2
        s = stern_brocot(n)
    end while
    idx[i] = k
end for
puts(1,"indexes of 1..10:")
?idx
puts(1,"index of 100:")
while 1 do
    k = find(100,s)
    if k!=0 then exit end if
    n *= 2
    s = stern_brocot(n)
end while
?k
s = stern_brocot(1000)
integer maxgcd = 1
for i=1 to 999 do
    maxgcd = max(gcd(s[i],s[i+1]),maxgcd)
end for
printf(1,"max gcd:%d\n",{maxgcd})