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Aug
8
comment How to count the $r$-tuples of subsets of $\{1,\dots,n\}$ that are cyclically disjoint?
Yes, that is right! 12 was a mistake.
Aug
8
comment How to count the $r$-tuples of subsets of $\{1,\dots,n\}$ that are cyclically disjoint?
And I know the next is 12, so the sequence is 2,3,4,7, 12,...
Aug
8
comment How to count the $r$-tuples of subsets of $\{1,\dots,n\}$ that are cyclically disjoint?
a nice view, thanks.
Aug
7
comment How to count the $r$-tuples of subsets of $\{1,\dots,n\}$ that are cyclically disjoint?
no, the condition is not Si∩Sj=∅ for any i and j, but for j=i+1 and so on.
Aug
7
asked How to count the $r$-tuples of subsets of $\{1,\dots,n\}$ that are cyclically disjoint?
Jul
22
comment How many different choice of sets?
This is very clear, thank you!
Jul
22
comment How many different choice of sets?
this is definitely true, but the problem is how to simplify it.
Jul
19
awarded  Curious
Jul
18
comment How many different choice of sets?
could you please explain a bit why is that?
Jul
18
comment How many different choice of sets?
$i≠j⇒Si∩Sj=∅$ is not demanded. Only when $i=j+1,Si∩Sj=∅$ is demanded. And permutations of $S_i$ is counted.
Jul
18
revised How many different choice of sets?
deleted 2 characters in body
Jul
18
awarded  Commentator
Jul
18
comment How many different choice of sets?
Sorry I do forget to add the condition that S_i is nonempty. But I do not think the first answer is correct anyway.
Jul
18
revised How many different choice of sets?
added 30 characters in body
Jul
18
asked How many different choice of sets?
Jul
16
revised How many positive integer solutions are there to the inequality $x_1+x_2+…+x_r\le n$?
added 122 characters in body
Jul
16
comment How many positive integer solutions are there to the inequality $x_1+x_2+…+x_r\le n$?
smart answer! Thank you!
Jul
16
asked How many positive integer solutions are there to the inequality $x_1+x_2+…+x_r\le n$?
Jan
25
answered edge coloring of a specific graph
Jan
24
comment edge coloring of a specific graph
Yes, Hagen's explanation is what I really mean.