I have 20 different coloured bangles.
Customers buy 60, in any combination.
(e.g. 60 of same colour, 5 each of all 20 colours, etc)
How many different combinations are possible?
(I realise it's somewhere between 20 factorial and 60 factorial, but then I'm stuck.)
Expressing the answer in the form n.nn x 10 to power y would be very helpful.