function output_sum = task_one(start_element_value, end_element_index, constant)
%% HOW TO
%     start_element_value - first a element
%     end_element_index - n (how many values of elements we should calculate)
%     constans - m constans added to each elemect according to formula:
%     a(n)=a(n-1)+m
%     output - vector with calculeted elements
%     element - current callculeted element 
%% MAIN CODE
    output(1,1) = start_element_value ;
    element =  output(1,1); % Initialization of a1
    for step=2:1:end_element_index % calculations starts for a2 element
        element = element + constant; % a(n) = a(n-1) + m
        output(1, step) = element; % append calculated value on an index
    end
    output_sum = sum(output);
end