Question

find the pattern 1,5,30,210,1680

Answer 1

Well to go from the 1st to the 2nd you multiply by 5, from the 2nd to 3rd you multiply by 6 and so on.

Answer 2

One way to write it mathematically is
\[ a_1 = 1 \\
a_n = (n+3)a_{n-1} \]
For example, the 4th number is:
\[ a_4 = (4+3)a_{4-1} = 7a_3 = 7((3+3)a_{3-1}) = 42a_2 = 42((2+3)a_1) = 42*5*1 = 210 \]

Answer 3

thanks