2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/72582We give a short proof of the result that all the coefficients of the series (1-x)(1-x^2)(1-x^3)(1-x^5)(1-x^8)(1-x^13)(1-x^21)... are equal to -1, 0, or 1, and most of them are equal to 0.4 pagesCombinatoricsNumber Theory05A17, 11B39, 11P81text