Serial.println(F("*\n**\n***\n****\n*****\n******\n*******\n********\n*********\n**********"));
Will not teach you anything about for loops, of course !
Serial.println(F("*\n**\n***\n****\n*****\n******\n*******\n********\n*********\n**********"));
Will not teach you anything about for loops, of course !