Every story and comment from the Hacker News API, in a layout borrowed from 2001.
A comment on Generating all permutations, combinations, and power set of a string (2012). Parent comment
(x + y)^n = sum{k=0,n} (n choose k) x^(n-k) y^k
And since a powerset is:
sum{k=0,n} (n choose k)
The way we can turn the first equation into a powerset is by setting x=1 and y=1, hence:
2^n = sum{k=0,n} (n choose k)
There are no comments on this comment yet.
(x + y)^n = sum{k=0,n} (n choose k) x^(n-k) y^k
And since a powerset is:
sum{k=0,n} (n choose k)
The way we can turn the first equation into a powerset is by setting x=1 and y=1, hence:
2^n = sum{k=0,n} (n choose k)