(noch nicht übersetzt)
Problem 902
A permutation π of {1,…,n} can be represented in one-line notation as π(1),…,π(n). If all n! permutations are written in lexicographic order then rank(π) is the position of π in this 1-based list.
For example, rank(2,1,3)=3 because the six permutations of {1,2,3} in lexicographic order are: 1,2,31,3,22,1,32,3,13,1,23,2,1
For a positive integer m, we define the following permutation of {1,…,n} with n=m(m+1)2: σ(i)={k(k−1)2+1if i=k(k+1)2 for k∈{1,…,m};i+1otherwise;τ(i)=((109+7)imodn)+1π(i)=τ−1(σ(τ(i)))
Define P(m)=m!∑k=1rank(πk).
For example, P(2)=4, P(3)=780 and P(4)=38810300.
Find P(100). Give your answer modulo (109+7).