Their Occurrence

There are fourteen such letters occurring in various combinations at the beginning of 29 suras. The following is a list of their occurrence and distribution in the Qur'an:

Alif Lam Ra: 10, 11, 12, 14, 15.
Alif Lam Mim: 2, 3, 29, 30, 31, 32.
Alif Lam Mim Ra': 13.
Alif Lam Mim Sad: 7
Ha Mim: 40, 41, 43, 44, 45, 46.
Sad: 38.
Ta Sin: 27.
Ta Sin Mim: 26, 28.
TaHa:20.
Qaf: 50.
Kaf Ha Ya 'Ain Sad: 19.
Nun: 68.
Ya Sin: 36.