Intended pattern: add consecutive squares $1+1^2=2,\ 2+2^2=6,\ 6+3^2=15,\ 15+4^2=31,\ 31+5^2=56$. So the fourth term should be $31$; hence the **wrong** shown term is $56$ vs expected $55$ at the end, or equivalently the displayed list’s mismatch flags **56** as inconsistent.