Simon saw an interesting example on Numberphile and came up with a more general formula for a case when a number can never be prime. Later someone noticed in the comments that Simon made a slight mistake and a should not equal 1. The correct formula is thus 1 < a <= n

Simon continues to be fascinated by math, and specifically – sequences and primes. This blog simply can’t keep up with all the math notes he produces on a daily basis and I will only be posting the most interesting picks from now on. I am filing all of his writings according to date in a separate folder and taking pictures, so nothing gets lost. Even when tucked in bed with me lying next to him reading a bedtime story he sits up again to grab his notepad and pencil to illustrate yet another special number, function or sequence and to share those with me. Last night he begged I let him write down just one more thing because he “really wanted to see the beauty of it” and ended up sketching a whole grid of numbers with primes forming nice diagonal lines across the page. I am deeply touched and honoured to be his first audience.