listfor(n, 1, 20, (((10^n - 1) / 9) * 7) / (10^n)
Sum ==(0.7, 0.77, 0.777, 0.7777, 0.77777, 0.777777, 0.7777777, 0.77777777, 0.777777777, 0.7777777777, 0.7777777777 7, 0.7777777777 77, 0.7777777777 777, 0.7777777777 7777, 0.7777777777 77777, 0.7777777777 777777, 0.7777777777 7777777, 0.7777777777 77777777, 0.7777777777 777777777, 0.7777777777 7777777777)==15 + 38/81
