It's the squares of the natural numbers starting with 1 multiplied by the odd numbers starting with 3: 1²×3 = 1×3 = 3 2²×5 = 4×5 = 20 3²×7 = 9×7 = 63 4²×9 = 16×9 = 144 5²×11 = 15×11 = 275 6²×13 = 36×13 = 468 Edwin