A pile of steel pipes has 3 steel pipes on the top layer, and there is a difference between two adjacent layers. There are 8 layers in total. How many steel pipes are there in this pile?
一堆钢管，最上面是一层是3根，每相邻的两层相差一根，共堆放了8层，这堆钢管有多少根．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">3 + 10</gadget>
<output>13</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">13 * 4</gadget>
<output>52</output>

<result>52</result>