This is probably the clearest guide to understanding Sundaram's Sieve but I feel like I'm either interpreting the instructions incorrectly or their's a minor error on this post.

First off, you state that I start with 4 and increment by 3, then I start at 7 ( adding 3 ) and increment by 5 ( adding 2 ). What's the need for any further incrementation to produce a third or more array of numbers when, through the subtracting you described, we will still get the same array of numbers ( 3, 5, 7, 9, 11, 13, etc. )

You say that if I apply 2n + 1 to the array of numbers generated ( 3, 5, 7, 9, 11, 13, etc. ), the answer will always be no, i.e. the number won't be prime. However, if I apply 2n + 1 to, lets say, 3, I get 7 which IS a prime number.

I'd also like to point out that the first number you state this is "not in the array" ( 5 ), is actually in the array! Applying 2n + 1 to the numbers not in the array still gives composite numbers as well such as 4. 2(4) + 1 = 9, which isn't a prime number.

I'd be extremely grateful if the explanation was either fixed or if my error in interpretation could be corrected.

This is probably the clearest guide to understanding Sundaram's Sieve but I feel like I'm either interpreting the instructions incorrectly or their's a minor error on this post.

First off, you state that I start with 4 and increment by 3, then I start at 7 ( adding 3 ) and increment by 5 ( adding 2 ). What's the need for any further incrementation to produce a third or more array of numbers when, through the subtracting you described, we will still get the same array of numbers ( 3, 5, 7, 9, 11, 13, etc. )

You say that if I apply 2n + 1 to the array of numbers generated ( 3, 5, 7, 9, 11, 13, etc. ), the answer will always be no, i.e. the number won't be prime. However, if I apply 2n + 1 to, lets say, 3, I get 7 which IS a prime number.

I'd also like to point out that the first number you state this is "not in the array" ( 5 ), is actually in the array! Applying 2n + 1 to the numbers not in the array still gives composite numbers as well such as 4. 2(4) + 1 = 9, which isn't a prime number.

I'd be extremely grateful if the explanation was either fixed or if my error in interpretation could be corrected.