Schur character orthogonality; Z_3 sum chi_0 = 3

Schur character orthogonality framework (Schur 1905 Sitzungsber Preuss Akad Wiss; Frobenius 1896). Setup: irreducible characters chi_i of finite group G satisfy sum_{g in G} chi_i(g) chi_j*(g) = |G| delta_{ij} - the *first orthogonality…