please solve using software R

(1) (a) Calculate the sum 1j and compare with n(n+1)/2 for n 1 J and compare with n(n+ 1)/2 for n 100, 200, 400, 800. (b) Referring to the above question, use the quick formula to compute 1j for 100, 200, 4 i= all values of n between 1 and 100. Store the 100 values in a vector. (2) Using rep) and seq) as needed, create the following vector: 1 2 3 4 5 2 3 4 5 6 34 5 6 745 678 56789