Vrijeme: 20:31

Najružniji lanac | The Ugliest Chain #4

Kruna Slavomirove kolekcije ipak je jedan zadatak koji je vidio još dok nije znao reći ni kosinus (Je li to izvor njegovih čudnih zanimacija? Tko bi znao...)
Neka je f(x)=(x^2+3x+2)^{\cos(\pi x)}. Pronađi zbroj svih prirodnih brojeva n za koje je \left |\sum_{k=1}^n\log_{10}f(k)\right|=1.

Crown jewel of Slavomir's collection is a problem that he saw long time ago, when he couldn't yet even spell cos (Might this be the source of his strange hobby? Who's to say...)
Let f(x)=(x^2+3x+2)^{\cos(\pi x)}. Find the sum of all positive integers n for which \left |\sum_{k=1}^n\log_{10}f(k)\right|=1 holds true.