Question

Write an explicit formula for An, the nth term of the sequence 7, 42, 252, ...

Answer 1

Explanation:

This is a geometric progression.

Givens

a1 = 7

r = 6

Formula

a_n = a1 * r^(n - 1)

a_n = 7 (6)^(n - 1)

Sample

Try n = 3

a_3 = 7*(6)^(3-1)

a_3 = 7*(6)^2

a_3 = 7 * 36

.a_3 = 252 which is exactly what it should be.