Evaluation of the Convolution Sums $\underset{\substack{   {(l,m)\in\mathbb{N}_{0}^{2}} {\alpha\,l+\beta\,m=n} }   }{\sum}\sigma(l)\sigma(m)$, where $\alpha\beta=44,52$
  The convolution sum, $\underset{\substack{ {(l,m)\in\mathbb{N}_{0}^{2}} {\alpha\,l+\beta\,m=n} } }{\sum}\sigma(l)\sigma(m)$, where $\alpha\beta=44,52$, is evaluated for all natural numbers $n$. We then use these convolution sums to determine formulae for the number of representations of a natural number by the octonary quadratic forms $a\,(x_{1}^{2} + x_{2}^{2} + x_{3}^{2} + x_{4}^{2})+ b\,(x_{5}^{2} + x_{6}^{2} + x_{7}^{2} + x_{8}^{2})$, where $(a,b)= (1,11),(1,13)$. 
Eb\'en\'ezer Ntienjem
math.NT