6-Letter Code

You will produce 6-letter codes using the 26 letters of the alphabet.

• A letter can be used only once in a code.
• Any two consecutive letters cannot be used in a single code.

In how many different ways can this be done?

If the same question was asked for the first four letters of the alphabet (A, B, C, D) and 2-letter codes, then the answer would be 6. (AC, CA, AD, DA, BD, DB).

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