A simple solution would be to define the function 

    \[CapitalPhi][m_, k_] := Cyclotomic[m, k]

Then write your comparision as

    myPi[n_] := Sum[KroneckerDelta[\[CapitalPhi][m, 1], m], {m, 1, n}]
    myPi[1001] == PrimePi[1001]

    (* Out[505]= True *)

Copying the first line as Latex gives the string

    \text{myPi}(\text{n$\_$})\text{:=}\sum _{m=1}^n \delta _{\Phi (m,1),m}

which shows up as

$$\text{myPi}(\text{n$\_$})\text{:=}\sum _{m=1}^n \delta _{\Phi (m,1),m}$$