Question 992528
<pre>
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

{{{a[n]=n^2*(2n+1)}}}

Edwin</pre>