14

Part of 1987 IMO Shortlist

Problems(1)

Number of words with n digits (IMO SL 1987-P14)

Source:

How many words with

n

digits can be formed from the alphabet

\{0, 1, 2, 3, 4\}

, if neighboring digits must differ by exactly one?
Proposed by Germany, FR.

symmetrycombinatoricsCombinatorics of wordscountingDigitsrecurrence relationIMO Shortlist