Guy, Richard K., Unsolved problems in number theory, third edition, Problem Books in Mathematics, Springer (2004), xviii+437 pp.; B2 "Almost perfect, quasi-perfect, pseudoperfect, harmonic, weird, multiperfect and hyperperfect numbers", printed p. 77: the weird-number questions, the last being "Can $\sigma(n)/n$ be arbitrarily large for weird $n$?", which Benkoski and Erdős conjecture has answer no, and for which Erdős offered a prize; a weird $n$ is abundant and not a sum of distinct proper divisors, so this question's constant $C$ is the conjectured bound on $\sigma(n)/n$. Library home: Guy 2004.