func fusc(n) is cached {

    return 0 if n.is_zero
    return 1 if n.is_one

    n.is_even ? fusc(n/2) : (fusc((n-1)/2) + fusc(((n-1)/2)+1))
}

say ("First 61 terms of the Stern-Brocot sequence: ", 61.of(fusc).join(' '))

say "\nIndex and value for first term longer than any previous:"
printf("%15s : %s\n", "Index", "Value");

var (index=0, len=0)

5.times {
    index = (index..Inf -> first_by { fusc(_).len > len })
    len = fusc(index).len
    printf("%15s : %s\n", index.commify, fusc(index).commify)
}