(1/(1*4))+(1/(4*7))+(1/(7*10))+(1/(10*13))+(1/(13*16))+ (1/(16*19)).
(1/(1*4))+(1/(4*7))+(1/(7*10))+(1/(10*13))+(1/(13*16))+(1/(16*19))．
<gadget id="calculator">1 * 4</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">4 * 7</gadget>
<output>28</output>

<gadget id="calculator">1 / 28</gadget>
<output>1/28 = around 0.035714</output>

<gadget id="calculator">7 * 10</gadget>
<output>70</output>

<gadget id="calculator">1 / 70</gadget>
<output>1/70 = around 0.014286</output>

<gadget id="calculator">10 * 13</gadget>
<output>130</output>

<gadget id="calculator">1 / 130</gadget>
<output>1/130 = around 0.007692</output>

<gadget id="calculator">13 * 16</gadget>
<output>208</output>

<gadget id="calculator">1 / 208</gadget>
<output>1/208 = around 0.004808</output>

<gadget id="calculator">16 * 19</gadget>
<output>304</output>

<gadget id="calculator">1 / 304</gadget>
<output>1/304 = around 0.003289</output>

<gadget id="calculator">(1/4) + (1/28) + (1/70) + (1/130) + (1/208) + (1/304)</gadget>
<output>6/19 = around 0.315789</output>

<result>6/19 = around 0.315789</result>