Last night my brother pitched me this math problem over dinner (which he later revealed came from this video). It goes something like this:
@@ -71,7 +49,14 @@Next, since I had no idea how I would go about counting the sequences, I looked at how I could group them, in hoping that would make them easier to count.
Arbitrarily, I decided to group the sequences by how many 2s were in them.
For the 5-stair staircase example, all of the possible sequences of 1s and 2s that sum to 5 look like:
-[1 1 2 1]+
[2 1 2]
[1 2 1 1]
[1 1 1 1 1]
[2 1 1 1]
[1 2 2]
[1 1 1 2]
[2 2 1][1 1 2 1] +[2 1 2] +[1 2 1 1] +[1 1 1 1 1] +[2 1 1 1] +[1 2 2] +[1 1 1 2] +[2 2 1]Grouping each sequence by the number of 2s in it yields the table:
@@ -313,6 +298,6 @@
This is the exact same function that appears on ProofWiki!
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