This is a spin off from another question.
4 letters are chosen and repetition is allowed so there are $26^4= 456976$ selections possible.
Now I am going to split this up.
Letters all different = 26∗25∗24∗23=358800
letters 2 the same= 26∗1∗25∗24∗4C2=93600
letters 3 the same=26∗1∗1∗25∗4C3=2600
Letters all the same=26
Add all these and I get 455026
WHY AM I SHORT???
Can anyone please tell me what selections I have missed out when I pulled apart the total?