
In This Way, but Nicely. Pattern Avoidance. Follow-Up. 207
DEFINITION 5.21 Let p be an n-permutation. The subsequence of p
consisting of
• all black and gray entries and
• all front entries that are preceded by at least one black entry and
• the entry n
is called the fundamental subsequence of p.
This means that permutations of the same class have identical fundamental
subsequences, and the part of these subsequences that is weakly on the left of
n is in the same position in each permutation belonging to the class.
DEFINITION 5.22 The classes C and C
are called similar if their
permutations have fundamental subsequences that are identical as permutation ...