Describe a sequence, discover a formula and verify it. Begin at the first unfamiliar idea; the prerequisite links help you find a shorter route. You can open any lesson.

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  1. R01

    Recursive sequences

    Compute terms and explain why initial conditions matter.

    Inside: Recursive sequences and initial conditions · Recursive versus explicit descriptions

  2. R02

    Classifying recurrence relations

    Classify a recurrence to select an appropriate method.

    Inside: Order and linearity · Homogeneous and non-homogeneous recurrences

  3. R03

    First-order linear recurrences

    Transform a first-order recurrence and verify its explicit formula.

    Inside: Arithmetic and geometric cases · Shifting a fixed point · Telescoping and variable forcing

  4. R04

    Nonlinear recurrences and substitutions

    Find a substitution suggested by the recurrence rather than guessing at random.

    Inside: Reciprocal substitutions · Factoring a recurrence · Invariants and domain restrictions

  5. R05

    Second-order linear recurrences

    Solve a second-order recurrence and justify the resulting expression.

    Inside: Characteristic roots · Distinct and repeated roots · Initial-value verification

  6. R06

    Higher-order linear recurrences

    Explain how the order and root multiplicities control the general form.

    Inside: Higher-order recurrences · Repeated roots and enough initial conditions

  7. R07

    Non-homogeneous recurrences

    Choose a valid particular form and adjust it when it overlaps the homogeneous part.

    Inside: Particular plus homogeneous solutions · Resonance · Verifying the combined solution

These original lessons introduce the methods and give practice with solutions. A single short session is not a full assessment of Olympiad readiness. Build depth through the written challenges and your country’s official past papers.