bro ti krutoi

https://docs.python.org/3/reference/expressions.html#shifting-operations

I didn't know that << existed!

That's cool though

I did 4.5 :)

sum(x^k,{k,1,infinity})=1/(1-x)
Derivative of x on both sides,→
sum(kx^(k-1))=1/(1-x)^2
then
sum(kx^k)=x/(1-x)^2
The domain of convergence of the series is (-1,1)

Thanks! That's good to know. That would certainly make the expression a bit cleaner.

Best solution imho. But because (almost) all meta characters loose their special meaning within a bracket expression, you don't need the 2nd and 4th backslash.

n10 is only chosen for passing the tests, so it's not a valid limit for large n (i had chosen n7 :).

OK, I see. Thanks for the reference.

Hi Eric,

it's a bit shift operator, see e.g. https://wiki.python.org/moin/BitwiseOperators.

Cheers,
Enrico