It returns (up to normalizing constant) the mass assigned to each positive integer or a vector of integers by Rissanen's universal prior for positive integers
Usage
rissanen(n)
Arguments
n
a vector of positive integers
Value
The mass assigned to each positive integer in the input vector of integers n by Rissanen's universal prior for positive integers
$$Q(n)=2^{-\log^*(n)} \qquad n>0$$
where
\(\log^*(x)= \log(x)+\log( \log (x)) + \log( \log (\log (x)))....\)
where the sum involves only the non-negative terms.
Notice that masses are not normalized hence they do not add to one,
but to a finite positive real constant
$$c = \sum_{n=1}^\infty Q(n)$$
Details
Rissanen's universal prior on positive integers is one of the default options for eliciting a noninformative prior distribution on the unknown population size \(N\). It is a proper prior with tails of the order between \(1/N\) and \(1/N^2\)
References
Rissanen, J. (1983) A universal prior for integers and estimation by minimum description length. Ann. Statist. 11, no. 2, 416-431