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5 votes
1 answer
213 views

Partition an $(2n+1)$-permutation into two parts in which there are no three consective elements in given sequences

Let $a_1a_2\ldots a_{2n+1}$ ($n\geq 2$) be a given permutation of the numbers from $1$ to $2n+1$ and let $\alpha_i=\{i,i+1,i+2\},~1\leq i\leq 2n-1$ $\alpha_{2n}=\{2n,2n+1,1\}$ $\alpha_{2n+1}=\{2n+1,1,...
W. Paul Liu's user avatar
2 votes
1 answer
184 views

Given $\pi$ permutation on $\{1,\dotsc,n\}$, what is the sign of a permutation of $\{2,\dotsc,\hat\jmath,\dotsc,n\}$?

This question is related to my other question Sign of the permutation which brings a subsequence back to its original form. Suppose I have a complete ordered set $\{a_{1},\dotsc,a_{2n}\}$ and take $\...
InMathweTrust's user avatar
1 vote
1 answer
102 views

Sign of the permutation which brings a subsequence back to its original form [closed]

I have the following question, which I am thinking about for days now and can't get the answer right. I have a sequence of elements in this order $x_{1},x_{2},...,x_{2n}$, $n \ge 1$ and then I perform ...
InMathweTrust's user avatar
45 votes
5 answers
3k views

How many rearrangements must fail to alter the value of a sum before you conclude that none do?

This will not be altogether unrelated to this earlier question. For which classes $C$ of bijections from $\{1,2,3,\ldots\}$ to itself is it the case that for all sequences $\{a_i\}_{i=1}^\infty$ of ...
Michael Hardy's user avatar