A Fibonacci sequence was a sequence of numbers that included 34, 55, and 89. (PROSE: Daisy Chain) The Twelfth Doctor identified 55 as the tenth Fibonacci number. (TV: Flatline [+]Jamie Mathieson, Doctor Who series 8 (BBC One, 2014).)
According to Saul, daisies had petal numbers in line with the Fibonacci sequence. (PROSE: Daisy Chain [+]Xanna Eve Chown, Short Trips: 2040 (Short Trips short stories, 2004).)
When Professor Jeffrey Broderick received a bottle of malt laced with a hallucinogen from Sir Toby Kinsella in 1964, it caused him to recite the Fibonacci sequence ad infinitum in order to keep himself occupied. (AUDIO: Artificial Intelligence [+]Matt Fitton, Counter-Measures: Series 1 (Counter-Measures, Big Finish Productions, 2012).)
The Weave's life cycle was similar to a Fibonacci sequence, with each name a successive number added to the last. When the Eleventh Doctor met a Weave named 6011, she confirmed that the Weave before her was 3715, and the one after her was 9726. (PROSE: The Glamour Chase [+]Gary Russell, BBC New Series Adventures (BBC Books, 2010).)
Whilst resisting the Keltin's gas, Adric first recited prime numbers before reciting the Fibonacci sequence. (AUDIO: The Star Men [+]Andrew Smith, Main Range (Big Finish Productions, 2017).)