Combinations for $2n$ distinct kids in $2n$ distinct seats ( + condition )

Asked Mar 01 '20 at 17:54

Active Mar 01 '20 at 18:04

Viewed 19 times

Given $2n$ labeled kids, $2n$ labeled seats, how many options are there to place the kids in the seats such that every odd-numbered kid with index $1 \leq i \leq n$ sits to the right (not necessarily adjacent) of the kid labeled as $2i.$

I'm stumped, any explanation is appreciated.

edited Mar 01 '20 at 18:04

amWhy

209,954

asked Mar 01 '20 at 17:54

woraday886

Use LaTeX please. https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference – Michael Rozenberg Mar 01 '20 at 17:56
Have you though about using inclusion-exclusion? – saulspatz Mar 01 '20 at 18:07
He can not answer you@saulspatz – nonuser Mar 01 '20 at 18:13

Combinations for $2n$ distinct kids in $2n$ distinct seats ( + condition )

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