Was it this theorem of Lagrange's that you had in mind https://en.wikipedia.org/wiki/Lagrange%27s_theorem_(group_theory) https://en.wikipedia.org/wiki/Lagrange%

Was it this theorem of Lagrange's that you had in mind https://en.wikipedia.org/wiki/Lagrange%27s_theorem_(group_theory) https://en.wikipedia.org/wiki/Lagrange%27s_theorem_(group_th... ?