(1/2)+(1/(2+3))+(1/(2+3+4))+(1/(2+3+4+5))+…+(1/(2+ 3+4+...+19+20)).
(1/2)+(1/(2+3))+(1/(2+3+4))+(1/(2+3+4+5))+…+(1/(2+3+4+…+19+20))．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 22</gadget>
<output>1/22 = around 0.045455</output>

<gadget id="calculator">(1/3) - (1/22)</gadget>
<output>19/66 = around 0.287879</output>

<gadget id="calculator">(1/2) + (19/66)</gadget>
<output>26/33 = around 0.787879</output>

<gadget id="calculator">(2/3) * (26/33)</gadget>
<output>52/99 = around 0.525253</output>

<gadget id="calculator">(1/2) + (52/99)</gadget>
<output>203/198 = around 1.025253</output>

<result>203/198 = around 1.025253</result>