5 = 4+1 = 2²+1 = 1st even natural number squared plus 1. 17 = 16+1 = 4²+1 = 2nd even natural number squared plus 1. 37 = 36+1 = 6²+1 = 3rd even natural number squared plus 1. = +1 = ²+1 = th even natural number squared plus 1. 101 = 100+1 = 10²+1 = 5th even natural number squared plus 1. I'll bet you can fill in the boxes yourself. Edwin