Find closed formula for an.

1. Iteration (Proof by Induction)
2. Linear homogeneous recursive relation with constant coefficiens (LHRC)
   find the roots of equation t₂+c₁t+C₂
   then where exist constants b, d such that a_n = br₁ⁿ+dr₂ⁿ, for n >= 0

Recursive Relation, Honoi Tower, LHRC