Discrete Mathematics

Question

Conjecture a simple formula for an if the first terms of the sequence an are 1,7, 25, 79, 241, 727, 2185, 6559, 19681, 59047.

Answer 1

If you just calculate differences, the answer is obvious. Differences are 6, 18, 54, ...

Then, if the first term is a₀, the series is defined as a_n = a_n-1 + 2*3ⁿ