What is the rule for 1-5-13-25-41-61?

The sequence 1, 5, 13, 25, 41, 61 follows a pattern where each term increases by a series of consecutive odd numbers. Specifically, the differences between consecutive terms are 4, 8, 12, 16, and 20, which are successive multiples of 4 (4×1, 4×2, 4×3, 4×4, 4×5). Thus, the next difference would be 24 (4×6), leading to the next term being 61 + 24 = 85.