we are supposed to crete an array u which has the mentioned sequence in ascending order. for the return part, given input is an index and its supposed to return the element from that index in the array.
This is my understanding.
I'm able to run my solution in difference compiler (programmiz) and get correct output for all the mentioned tests, however it's getting timed out here

I'm confused at the example and how the function returns 22 for dbl_linear(10).
I don't think I'm understanding the task correctly particularly where it asks for "of the ordered (with <) sequence u".

Can someone please help me understand what I'm supposed to be doing and how the function returns 22 for an input of 10.

Thanks in advance

Duh! Nice one.