Take the 2-minute tour ×  In how many ways you can make a stack
of N disks, such that:    1. Bottom disk always has radius 1
2. A disk can be placed on the stack if it radius is <= (maximum
of all disk radii below it + 1)  You are given an infinite
supply of disks with all radius.  I thought of couple of
counting approach but that has lots of overlapping in the
already counted solution and I am not able to get rid of it. :(
share|improve this question This isn’t quite clear. (1) Do all
the disks have integer radii? (2) Do you have an infinite supply
of disks of each radius, or do you have only one disk for each
of the infinitely many possible radii? –  Brian M. Scott Apr 5
'12 at 7:00 @Brian : I think it is the Towers of Hanoi –  Arjang
Apr 5 '12 at 7:05 @Arjang: No, it very clearly is not the Towers
of Hanoi. –  Brian M. Scott Apr 5 '12 at 7:12 @Arjang:
Definitely not Hanoi. There the largest disk go below, here
disks may be bigger than the one below. Login: A lot is not
clear though. Is there exactly on