MathDB

4.3

Part of 2013 Saudi Arabia Pre-TST

Problems(1)

no of permutations of 1,2,..., n with s_i > s_j$ for all i >= j + 3 when n =5, 7

Source: 2013 Saudi Arabia Pre-TST 4.3

9/13/2020
How many permutations (s1,s2,...,sn)(s_1, s_2,...,s_n) of (1,2,...,n)(1,2 ,...,n) are there satisfying the condition si>sjs_i > s_j for all i≥j+3i \ge j + 3 when n=5n = 5 and when n=7n = 7?
combinatoricspermutation