Collatz Conjecture
113598
Collatz optimization
83841
Mutual Exclusion Problem
146933
Proving bipartition in a connected planar graph
147485
A conjecture about numbers of the form $10^{m}(2^{k}−1)+2^{k-1}−1$, where $m$ is the number of decimal digits of $ 2^{k-1}$.
73287
Project Euler Question 14 (Collatz Problem)
136449
Combinatorics problem on $20$ people, $12$ months, and distinguishable groups
140153
Conjectures Involving floor(x)/piecewise continuity with regards to Integration and Differential Equations
41726
Musical and combinatorial proof
99900
Pigeonhole principle application
86067
A Variation of the even-town odd-town problem
107964
Simple combinatorics problem.
23523
Two problems on number theory
116153
The Notorious Triangle Problem
63571
The Mississipi counting problem, this time in circle
144571
A conjecture including binomial coefficients
92193
Problem from Herstein on group theory
12291
Two envelope problem revisited