In mathematics, the Lucas sequences U n {\displaystyle U_{n}} and V n {\displaystyle V_{n}} are certain constant-recursive integer sequences that satisfy the recurrence relation x n = P ⋅ x n − 1 − Q ⋅ x n − 2 {\displaystyle x_{n}=P\cdot x_{n-1}-Q\cdot x_{n-2}} where P {\displaystyle P} and Q {\displaystyle Q} are fixed integers. Wikipedia