(In reply to
re(2): Solution by Charlie)
My chart is wrong, just not in the way you pointed out. My chart if of "subsets" not "words." I then multiplied each number by n! to get the number of words.
The disagreement is how I interpreted "no neighboring letters that neighbor each other." I discounted words like adb which contains a and b  neighboring letters even though they don't neighbor each other.
My solution is then to the slightly simpler problem:
How many "words" (i.e, ordered subsets from (a,b,c, … x,y,z))
contain no neighboring letters in the English
ABC (26 letters)?

Posted by Jer
on 20140326 09:21:08 