Probability for n tables: [1-(n-2)p]*[1-(1-(n-1)p)
n] + Sum
k=1 to n-2 kp[1-(k-1)p]
So for 4 tables that's p + 2p(1-p) + (1-2p)[1-(1-3p)^4] =~ 1.1267% or about 1 in 88.756
By comparison, 15p = 1 in 88.4
For 5 tables my formula says ~1.948% or 1 in 51.34
Compare to 26p = 1 in 51
There's an easy way to remember my formula from last post (for determining the #'s 7, 15, 26, 40, ...)
It's like n! except after one multiplication, the rest of the * signs become + signs.
15 = 4*3+2+1
26 = 5*4+3+2+1
Edit: it's OEIS
A005449, "second pentagonal numbers".
Quote:
Also number of cards to build an n-tier house of cards. - Martin Wohlgemuth (mail(AT)matroid.com)
Last edited by heehaww; 11-16-2015 at 11:05 AM.