Problem #47: Checker Pattern

How many turquoise squares will be required to build the twentieth figure in this pattern? 
X     X X     X X X     X X X X
       X       X X       X X X 
      X X     X X X     X X X X
               X X       X X X 
              X X X     X X X X
                         X X X 
                        X X X X
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