不包括Sundaram筛号

Question

I'm working on implementing the Sieve of Sundaram .

The first step is to get a list of Integer's such that:

i, j are Natural Numbers, 1 <= i <= j

i + j + 2*i*j <= n

Here's my function. It's supposed to generate a list of tuples of all (i, j) 's that match the above restrictions.

numsToRemove :: Integer -> [(Integer, Integer)]
numsToRemove n = [ (i, j) | i <- [1..n], j <- [1..n], i <= j, i >= 1, j >= 1, 
                            i * j + 2*i*j <= n]

But I'm getting non-primes in my answer. Excluding my other work, I think that I'm making a mistake in generating this list of Integers.

Please let me know what I'm doing wrong.

Answer 1

Your function checks for i * j + 2*i*j <= n but your definition asks for i + j + 2*i*j <= n . There is a * that should have been a + .