# Mathematica, <s>62</s> <s>61</s> 60 bytes <sup>*Saved 2 bytes due to [@MartinEnder](http://ppcg.lol/users/8478).*</sup> MatchQ[{a:1...,b___}/;{b}==-{a}]@*Differences@*IntegerDigits Composition of functions. Takes a number as input and returns `True` or `False` as output.