fastfunc sumprop num .
   if num = 1 : return 0
   sum = 1
   root = sqrt num
   i = 2
   while i < root
      if num mod i = 0
         sum += i + num / i
      .
      i += 1
   .
   if num mod root = 0
      sum += root
   .
   return sum
.
func$ class k .
   oldk = k
   newk = sumprop oldk
   oldk = newk
   seq[] &= newk
   if newk = 0 : return "terminating " & seq[]
   if newk = k : return "perfect " & seq[]
   newk = sumprop oldk
   oldk = newk
   seq[] &= newk
   if newk = 0 : return "terminating " & seq[]
   if newk = k : return "amicable " & seq[]
   for t = 4 to 16
      newk = sumprop oldk
      seq[] &= newk
      if newk = 0 : return "terminating " & seq[]
      if newk = k : return "sociable (period " & t - 1 & ") " & seq[]
      if newk = oldk : return "aspiring " & seq[]
      for i to len seq[] - 1
         if newk = seq[i] : return "cyclic (at " & newk & ") " & seq[]
      .
      if newk > 140737488355328 : return "non-terminating (term > 140737488355328) " & seq[]
      oldk = newk
   .
   return "non-terminating (after 16 terms)  " & seq[]
.
print "Number classification sequence"
for j = 1 to 12
   print j & ": " & class j
.
for j in [ 28 496 220 1184 12496 1264460 790 909 562 1064 1488 15355717786080 ]
   print j & ": " & class j
.