Start at 4. Create a pattern that multiplies each number by 5. Stop when you have five numbers.

Call A the first number, then the pattern will be: term number 1 A 2 5A 3 (5^2) A 4 (5^3) A 5 (5^4) A Then, you realize that you can obtain any term by doing An = A * (5) ^ (n-1), or A * (5^n) / 5