(1/(3*7))+(1/(7*11))+(1/(11*15))+(1/(15*19))+(1/(19*23)).
(1/(3*7))+(1/(7*11))+(1/(11*15))+(1/(15*19))+(1/(19*23))．
<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<gadget id="calculator">1 / 21</gadget>
<output>1/21 = around 0.047619</output>

<gadget id="calculator">7 * 11</gadget>
<output>77</output>

<gadget id="calculator">1 / 77</gadget>
<output>1/77 = around 0.012987</output>

<gadget id="calculator">11 * 15</gadget>
<output>165</output>

<gadget id="calculator">1 / 165</gadget>
<output>1/165 = around 0.006061</output>

<gadget id="calculator">15 * 19</gadget>
<output>285</output>

<gadget id="calculator">1 / 285</gadget>
<output>1/285 = around 0.003509</output>

<gadget id="calculator">19 * 23</gadget>
<output>437</output>

<gadget id="calculator">1 / 437</gadget>
<output>1/437 = around 0.002288</output>

<gadget id="calculator">(1/21) + (1/77) + (1/165) + (1/285) + (1/437)</gadget>
<output>5/69 = around 0.072464</output>

<result>5/69 = around 0.072464</result>