Michael Kleber's comment
<<
. . . (Pretending that pi is a string of random digits
and other such falsities...)
>>
got me thinking. Suppose we have a probability distribution D
on the set S of all countable sequences of decimal digits.
And suppose that for all *finite* sets of indices {i_1 < ... < i_n},
the corresponding marginal distribution is uniform on {0,...,9}^n.
1. Does it then follow that D is uniform on S ???
1a. Is there a way countably many variables can be correlated
even if no finite subset of them are?
Related question:
I like considering numbers' "digits" in "factorial" base.
For x in [0,1], I mean by this writing
x = a_1/2! + a_2/3! + ... + a_n/(n+1)! + ...
where each a_n is an integer such that 0 <= a_n <= n. Luckily,
1/2! + 2/3! + 3/4! ... = 1/2 + 1/3 + 1/8 + 1/30 + 1/144 +... = 1.
2. Is pi normal to the factorial base? Here I mean only the fractional
part of pi. I.e., for any finite set of indices {i_1 < i_2 < ... < i_n},
does the joint distribution on
a_(k + i_1)/(k + i_1+1)! , , ... , a_(k + i_n)/(k+i_n+1)!
approach a uniform cdf on [0,1]^n as k -> oo ?
N.B. It's easy to check that e would definitely NOT be normal to the
factorial base.
--Dan