What is the recursive formula for the sequence 4, 16, 36, 64,

Unrecursively, that's

A quadratic will have a linear first difference:

So we get

f(1) = 4

f(n+1) = f(n) + 8n + 4

its 0.1 miles per minute

if you are saying purchasing 3 social media ads and one newspaper ad counts as one purchase then there are:

6 purchases

if you are asking how many of each then:

18 social media ads

6 newspaper ads