MathDB
straight permutation

Source: created by Valentin Vornicu - Romanian TST 2003, problem 17

February 10, 2004
inequalitiessymmetrycombinatorics proposedcombinatorics

Problem Statement

A permutation σ:{1,2,,n}{1,2,,n}\sigma: \{1,2,\ldots,n\}\to\{1,2,\ldots,n\} is called straight if and only if for each integer kk, 1kn11\leq k\leq n-1 the following inequality is fulfilled σ(k)σ(k+1)2. |\sigma(k)-\sigma(k+1)|\leq 2. Find the smallest positive integer nn for which there exist at least 2003 straight permutations. Valentin Vornicu