(99/(1*2*3*4*5*6))+(171/(2*3*4*5*6*7))+(261/(3*4*5*6*7* 8))+...+(2745/(15*16*17*18*19*20)).
(99/(1*2*3*4*5*6))+(171/(2*3*4*5*6*7))+(261/(3*4*5*6*7*8))+…+(2745/(15*16*17*18*19*20))．
<gadget id="calculator">1 * 3 * 5</gadget>
<output>15</output>

<gadget id="calculator">3 / 15</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">16 * 18 * 20</gadget>
<output>5_760</output>

<gadget id="calculator">3 / 5_760</gadget>
<output>1/1_920 = around 0.000521</output>

<gadget id="calculator">(1/5) - (1/1_920)</gadget>
<output>383/1_920 = around 0.199479</output>

<result>383/1_920 = around 0.199479</result>