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Arithmetic sequence: aₙ = a₁ + (n−1)d; common difference d is constant. Geometric: aₙ = a₁ × r^(n−1); common ratio r is constant. Fibonacci: aₙ = aₙ₋₁ + aₙ₋₂. Identify the type by checking if differences or ratios are constant. Sum of arithmetic series: n(a₁+aₙ)/2. Geometric series sum: a₁(1−rⁿ)/(1−r). Sequences appear in nature, finance, and algorithm analysis.
Sum = 120.000000