Well, everybody here knows, that best scheme is 0(X*i+) . But lot of us get WA1. I've found why we fail like this. The last line of output shouldn't contain line break, so I've changed string "X\n*\ni\n+\n" to "\nX\n*\ni\n+" and got AC.

OMG. It is very strange :)
      for (int i = 1; i <=n; i++ ){
         out.printf("X%n*%n%d%n+%n",i);
      }
(Java)