Sample Size and Simulation for Negative Binomial Outcomes // Provides tools for planning and simulating recurrent event trials with overdispersed count endpoints analyzed using negative binomial (or Poisson) rate models. Implements sample size and power calculations for fixed designs with variable accrual, dropout, maximum follow-up, and event gaps, including methods of Zhu and Lakkis (2014) doi:10.1002/sim.5947 and Friede and Schmidli (2010) doi:10.3414/ME09-02-0060 as well as extensions for score-test sizing and gaps between events. Supports group sequential monitoring by building on the 'gsDesign' package. Includes recurrent-event simulation utilities (including seasonal rates), interim data truncation, Wald and score-test inference for rate ratios, and information estimation and sample size re-estimation with or without treatment-group labels.