Colorado Common Core Standards
CO.4.2. Patterns, Functions, and Algebraic Structures
4.2.1. Number patterns and relationships can be represented by symbols. Students can:
4.2.1.a. Generate and analyze patterns and identify apparent features of the pattern that were not explicit in the rule itself. (CCSS: 4.OA.5)
4.2.1.a.i. Use number relationships to find the missing number in a sequence.