MathCastle
Counting & ProbabilityHardCounting Strategies: Casework, Complementary & Overcounting

Counting Strategies: Casework, Complementary & Overcounting · Hard problem

How many nondecreasing functions f:{1,2,3,4}→{1,2,…,7}f:\{1,2,3,4\}\to\{1,2,\dots,7\} are there?