MathDB
Cubic sequence

Source: RMM 2016 Day 1 Problem 3

February 27, 2016
number theoryRMM

Problem Statement

A <spanclass=latexitalic>cubicsequence</span><span class='latex-italic'>cubic sequence</span> is a sequence of integers given by an=n3+bn2+cn+da_n =n^3 + bn^2 + cn + d, where b,cb, c and dd are integer constants and nn ranges over all integers, including negative integers. <spanclass=latexbold>(a)</span><span class='latex-bold'>(a)</span> Show that there exists a cubic sequence such that the only terms of the sequence which are squares of integers are a2015a_{2015} and a2016a_{2016}. <spanclass=latexbold>(b)</span><span class='latex-bold'>(b)</span> Determine the possible values of a2015a2016a_{2015} \cdot a_{2016} for a cubic sequence satisfying the condition in part <spanclass=latexbold>(a)</span><span class='latex-bold'>(a)</span>.