list comprehensions are faster than lambda expressions, great...

this should be the first upvoted, if users just took a while to see why it is 2 lines not 1.

brute force was voted more then this solution lol. This should go up^^!

:D :D :D

S - is the sum of a square's sides, than that sum (S) is multiplied by 4 and as a result you get a perimeter of squares.
So S(n) - is a length of nth square side.

And you need to write a function that will calculte 4 * S = 4 * ( S(0) + S(1) + .... + S(n) )

An IntStream. See https://docs.oracle.com/javase/8/docs/api/java/lang/CharSequence.html#chars--

Can someone explain this for me?
Say that S(n) is the nth term of the above sum. So S(0) = 1, S(1) = 1, S(2) = 2, ... , S(5) = 8
What does it mean nth term of the above sum, I understand it in a way that S(5) is the sum of perimeters of 5 such rectangles.

this is java-8, do they support java 8?

nice one

no problem super smart guy

Thank you! My fans

you are so clever Gigi, im astonished