GCSE Maths Practice: sequences

Question 7 of 12

This question tests identifying the recursive formula for triangular numbers.

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\( \text{What is the recursive rule for the sequence: } 1, 3, 6, 10, 15, ...? \)

Choose one option:

\( u_n = u_{n - 1} + n \) \( u_n = u_{n - 1} + 2 \) \( u_n = n(n + 1) \) \( u_n = 2n - 1 \)

Observe the differences between consecutive terms to find pattern.

Triangular numbers: each term is sum of natural numbers up to n.

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