What is the 51st number in a column of numbers arranged according to 1, 4, 7, 10, 13, ....
按1，4，7，10，13，…，排列的一列数中，第51个数是多少．
<gadget id="calculator">51 - 1</gadget>
<output>50</output>

<gadget id="calculator">50 * 3</gadget>
<output>150</output>

<gadget id="calculator">1 + 150</gadget>
<output>151</output>

<result>151</result>