I don t think it s equivalent to the sieve of eratosthenes even when the optimization of using only odds is used Here is what Sieve of Sundaram looks like where we loop at a 2i 1 and b 2j 1 instead of i and j n 1000000 limit initialize the sieve is prime 2 true is prime i i is odd i 3 n for all odd a such that 3 a and a n for all odd b such that a b and ab n is prime ab false while Sieve of Eratosthenes using only odd integers roughly looks like this only one line is added n 1000000 limit initialize the sieve is prime 2 true is prime i i is odd i 3 n for all odd a such that 3 a and a n if not is prime a continue only this has changed for all odd b such that a b and ab n is prime ab false This also shows that the Sieve of Sundaram is less efficient than the Sieve of Eratosthenes and that its complexity is n log n since 1 2 1 3 1 4 1 n grows asymptotically as log n compared to sieve of eratosthenes n log log n since 1 2 1 3 1 5 1 7 1 p grows asymptotically as log log n