A.L.M.R. (Alef. Laam. Mim. Ra.)
A.

L.

M.

R.

These initials prefix one chapter, No. 13, and the total frequency of occurrence of the four letters is 1482, or 19x78. The letter "Alef" occurs 605 times, "Laam" occurs 480 times, "Mim" occurs 260 times, and "Ra" occurs 137 times.