I've just wrote them an email with this idea=).

Redundant StringBuilder floor usage.

Or as an option, developers of this web site will have add something like load tests and show avg execution time near each sulution in such test. to give developerse oppotuniti competting in whose code is the most effective. And also add the fastest code filter in here. And the same to memory usage. Also such statistic may be useful to newbe.

This is a source of the exception when a result of Pow is higher tham double.

if n is int.MaxValue than stack overflow exception.=)

if n is int.MaxValue than stack overflow exception.=)

if n is int.MaxValue than stack overflow exception.=)
Repeat 7411 times.

BigInteger.Pow ?)
https://learn.microsoft.com/en-us/dotnet/api/system.numerics.biginteger.pow?view=net-7.0

https://learn.microsoft.com/en-us/dotnet/api/system.numerics.biginteger.pow?view=net-7.0

Use BigInteger.Pow instead.

In worst case O(n*l);
n is str length.
l is "aeiouAEIOU" length.
Am I misstaking?

Redundant Contains check.

True, it works well, and truly readable. Just a line of code!

O(n)+O(n) complexity?

O(n)+O(n) complexity?