syms q a x
f=a(q+1)*x(2)^q
y(2) = symsum(f, q, 0, m)

% Inputs , for example x=[1,2,3,..,10] and a=[5,6,7,8]

x=1:10
a=[5,6,7,8]

% m <= length(a)

m=3

% temporary matrices

[tx,ta] = meshgrid(x,a)
[~,tm]=meshgrid(x,0:m)
t=ta(1:m+1,:).*tx(1:m+1,:).^tm(1:m+1,:)

% y is your result and has equal elemnts to x matrix

y=sum(t,1)

% some outputs

y(2)
y(3)