link factors

procedure main(A)
   i := \A[1] | 20000
   every (n := seq()\i, m := seq(n)\(i-n)) do
       write((amicable(n,m),n)," : ",m)
end

procedure amicable(n,m)
   static cache
   initial cache := table()
   if n = m then fail
   if /cache[n] then every (cache[n] := 0) +:= (n ~= divisors(n))
   if /cache[m] then every (cache[m] := 0) +:= (m ~= divisors(m))
   return (cache[n] = m, cache[m] = n)
end