That is, 1+3+5+7+11+13+15=120; and 1+3=4+5=9+7=16+9=25+11=36+13=49+15=64, giving us the numbers 4, 9, 16, 25, 36, 49, 64, the squares of 2, 3, 4, 5, 6, 7, 8.