UNI_BRIDGE · Calculus · SEQ.INTRO

Sequences and recurrences

Intuition

Understand first, compress later.

Calculus studies change and accumulation through limiting processes.

Switch representations

Arithmetic sequencea₁ = 2, d = 3

terms aₙstep +3

A sequence is defined only for the natural numbers n = 1, 2, 3, … — which is why this plate shows separate dots on stems rather than a continuous curve; there is no term between two dots. Each step adds 3 (the recurrence), while the closed form gives any term directly: a_n = 2 + (n − 1)·3 = 3n − 1.

Formal view

You can sequences and recurrences when you can recognise the underlying objects, select valid rules and check each step for equivalence or logical implication.

Why does it work?

This skill sits on a prerequisite network. If a step is unstable, repair the missing prerequisite instead of merely doing more items of the same type.