Explanation:
yes, the other answer is correct.
just to explain a little bit more :
the sequence is clearly built by subtracting 6 from one element to the next.
in other words :
a1 = 45
a n = a n-1 - 6
in such a sequence you do the same operation/ calculation over and over again - once per new element.
the operation in this example is simple - as mentioned : subtract 6.
a1 just gives us a starting value (no operation done for for it) zu, the operation is done one time less than the running number of the element.
therefore, the general element generation algorithm/ formula is :
a n = a1 - (n-1)*6