1+5+9+13+17+...+2009=how much.
1+5+9+13+17+…+2009=多少．
<gadget id="calculator">1 + 2_009</gadget>
<output>2_010</output>

<gadget id="calculator">2_009 - 1</gadget>
<output>2_008</output>

<gadget id="calculator">2_008 / 4</gadget>
<output>502</output>

<gadget id="calculator">502 + 1</gadget>
<output>503</output>

<gadget id="calculator">503 / 2</gadget>
<output>503/2 = around 251.5</output>

<gadget id="calculator">2_010 * (503/2)</gadget>
<output>505_515</output>

<result>505_515</result>