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Dec
30
comment Puzzle: How Many Possibilities Are There Between Connected Points?
@BukLau you choose pairs one by one and then divide by number or orders we could choose these pairs in
Dec
30
comment Puzzle: How Many Possibilities Are There Between Connected Points?
Total number of possible connections in the $2n$ point problem is: $$\frac{1}{n!}\prod_{i=1}^n \binom {2i}{2}$$
Dec
9
awarded  Caucus
Nov
25
comment Distinguish between clockwise and counterclockwise polygon
If the polygon is convex it is enough to check the cross product of any two given consecutive edges, treated as vectors with the same origin. For polygon $ABCDE$ it would be $CB \times CD$
Nov
14
accepted What is a sparse subset?
Nov
14
reviewed No Action Needed Prove by induction for$ P(x)$
Nov
14
revised Is this combinatorial problem for noncommutative variables known?
added definition
Nov
14
suggested approved edit on Is this combinatorial problem for noncommutative variables known?
Nov
14
comment Is this combinatorial problem for noncommutative variables known?
Binomial(n, floor(n/2)) -> oeis.org/A001405 has description well fitting your problem: it is also the number of distinct strings of length n, each of which is a prefix of a string of balanced parentheses
Nov
14
comment What is a sparse subset?
@QiaochuYuan what does that mean in terms of subsets of vectors then?
Nov
14
answered Proof By Induction Fibonacci Numbers
Nov
14
revised Proof By Induction Fibonacci Numbers
improved formatting
Nov
14
suggested approved edit on Proof By Induction Fibonacci Numbers
Nov
14
asked What is a sparse subset?
Nov
9
awarded  Yearling
Sep
30
awarded  Explainer
Sep
24
awarded  Autobiographer
Nov
9
awarded  Yearling
Apr
2
answered How do I prove: $\cos (\theta + 90^\circ) \equiv - \sin \theta $
Feb
8
awarded  Revival