title: Algorithm Recurrence formula
body: <p>I am reading Algorithms in C++ by Robert Sedgewick. Basic recurrences section it was mentioned as This recurrence arises for a recursive program that loops through the input to eliminate one item
                                Cn = cn-1 + N, for N >=2 with C1 = 1.</p>
  
  <p>Cn is about Nsquare/2.  Evaluating the sum 1 + 2 +...+ N is elementary. in addition to this following statement is mentioned.
            " This result - twice the value sought - consists of  N terms, each of which sums to N +1</p>
  
  <p>I need help in understanding abouve statement what are N terms here and how each sums to
  N +1, aslo what does "twice the value sought" means.</p>
  
  <p>Thanks for your help</p>