Multiply a number by a sequence of numbers in a column

I'm trying to figure out how to multiply a number by a sequence of numbers that is auto generated for each cell in a column.

Example:

A1: 40 * 1 = 40
A2: 40 * 2 = 80
A3: 40 * 3 = 120

Selecting the first two or three and pasting down just repeats those same numbers.

Is there an easy way to accomplish this task?

Thank you
Mike

The only way I can figure is if you have your base number (40) in a cell by itself n(ie A1)
Then have your number sequence in another column (ie B)
Then write a formula where you make cell A1 absolute and drag the formula down.

Thanks for the suggestions but I found a simpler way that works for what I need.

Here it is if it helps anyone else down the road:

In A1:

=40*row(a1)

copy down....