Kata

I need to save some money to buy a gift. I think I can do something like that:

First week (W0) I save nothing on Sunday, 1 on Monday, 2 on Tuesday... 6 on Saturday, second week (W1) 2 on Monday... 7 on Saturday and so on according to the table below where the days are numbered from 0 to 6.

Can you tell me how much I will have for my gift on Saturday evening after I have saved 12? (Your function finance(6) should return 168 which is the sum of the savings in the table).

Imagine now that we live on planet XY140Z-n where the days of the week are numbered from 0 to n (integer n > 0) and where I save from week number 0 to week number n included (in the table below n = 6).

How much money would I have at the end of my financing plan on planet XY140Z-n?

Example:

finance(5) --> 105
finance(6) --> 168
finance(7) --> 252
finance(5000) --> 62537505000

Note:

your solution will be nicer without loops.