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Pure mathematics · Olympiad · university
Combinatorics
The art of counting without counting — and graphs, invariants, and pigeonholes.
10 chapters · 143 curated · 1,782 from open sources · 81.8 million generated
Chapters
Chapter 1Sets & logic95 problemsChapter 2Counting99 problemsChapter 3Permutations & combinations1,679 problems · 1,296 practiceChapter 4Binomial coefficients15 problems · 4,839 practiceChapter 5Inclusion–exclusion2 problems · 81.2 million practiceChapter 6Pigeonhole7 problems · 58,752 practiceChapter 7Invariants7 problemsChapter 8Generating functions0 problems · 9,136 practiceChapter 9Recurrences4 problems · 493.9 thousand practiceChapter 10Graph theory17 problems