Batir, N.2025-05-102025-05-1020080716-091710.4067/S0716-091720080001000062-s2.0-56149119777https://doi.org/10.4067/S0716-09172008000100006https://hdl.handle.net/20.500.14720/6512Let n be a positive integer. We prove nn+1e-n√2π/√n-α ≤ n! < nn+1e-n2√2π/√n-β with the best possible constants α = 1- 2π-2 = 0.149663... and β = 1/6 = 0.1666666... This refines and extends a result of Sandor and Debnath, who proved that the double inequality holds with α = 0 and β = 1.eninfo:eu-repo/semantics/openAccessBurnside'S FormulaFactorial NGamma FunctionStirling'SArticle271N/AQ397102