Sequences And Series

Let \(a_{1}=b_{1}=1, a_{n}=a_{n-1}+2\) and \(b_{n}=a_{n}+b_{n-1}\) for every

natural number \(n \geqslant 2\). Then \(\sum\limits_{n = 1}^{15} {{a_n}.{b_n}}\) is equal to ___________.