the first one is pretty easy to know so i dont have to say anything One less than a square: Its a square - 1 but heres an interesting way to do this. Example: 1x3=3 2x4=8 3x5=15 4x6=24 5x7=35 etc. One Less than a prime with some exceptions: Example: 1x4=4 4+1=5 2x5=10 10+1=11 3x6=18 18+1=19 4x7=28 28+1=29 5x8=40 40+1=41 6x9=54 54+1=55 (NOT A PRIME)
c2a
