Let's find the inflection points, we'll need to solve the equation for this
dn2d2f(n)=0(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
dn2d2f(n)=the second derivativen−(−1)nπ2−n2(−1)niπ+n22((−1)n+1)=0Solve this equationSolutions are not found,
maybe, the function has no inflections