Linear recurrence a_{n+k} + c_{k-1}a_{n+k-1} + ... = 0: characteristic-poly solution

Constant-coefficient linear recurrence of order k: a_{n+k} + c_{k-1}a_{n+k-1} + … + c_0 a_n = 0. Ansatz a_n = λⁿ reduces the recurrence to the characteristic polynomial χ(λ) = λ^k + c_{k-1}λ^{k-1} + … + c_0 = 0. With distinct roots λ_1,…