This is the code to raise each element of a matrix by its position index.

matrix_element_power.m

%simple/ easy-to-understand solution
function ans = matrix_pow(a)
  append=[]
  for i=1:numel(a)
    addi= a(i)^i
    append= [append addi]
  end
  sum(append)
end
    
%alternative and more efficient solution
function ans = matrix_pow(x)
    %numel indicates the number of elements in an array or a matrix
    %power command raises the power of the argument by the specified number (here 1:numel(x))
  sum(power(x(:)',1:numel(x))); 
end