Wigner 3-j symbol.
ThreeJSymbol[{j1, m1}, {j2, m2}, {j3, m3}]
ThreeJSymbol[{6, 0}, {4, 0}, {2, 0}]
→ Sqrt[5/143]ThreeJSymbol[{1 / 2, -1 / 2}, {1 / 2, -1 / 2}, {1, 1}]
→ -(1/Sqrt[3])With[{l1 = 4, m1 = 0, l2 = 3, m2 = 2, l3 = 3, m3 = 2}, Sqrt[((2 l1 + 1) (2 l2 + 1) (2 l3 + 1)/4 π)] ThreeJSymbol[{l1, 0}, {l2, 0}, {l3, 0}] ThreeJSymbol[{l1, m1}, {l2, m2}, {l3, -m3}]]
→ (-7*Sqrt[Pi])/22