Nov 23

Fibonacci Day

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Fibonacci Sequences in Nature
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"1, 1, 2, 3, 5, 8, 13, 21, 34, ..."

Fibonacci Day is November 23rd, as it has the digits "1, 1, 2, 3" which is first part of the Fibonacci sequence. The Fibonacci numbers appear everywhere in nature, from the leaf arrangement in plants, to the pattern of the florets of a flower, the bracts of a pinecone, the scales of a pineapple, as well in natural phenomenon, such as the shapes of spiral galaxies and hurricanes!

Fibonacci Day is celebrated November 23, using month-first notation 1-1-2-3, 11/23, because the Fibonacci series begins 1, 1, 2, 3, 5, 8, ... a pattern of counting where each number is the sum of the previous two.


As well as being prevalent in nature, Fibonacci Day recognises the importance and value of Italian mathematician Leonardo Fibonacci’s contributions to mathematics.


The pattern and colour of stitches in the tartan are based on both the sequence and the colours of the Italian flag.

Leonardo of Pisa, sometimes known as Leonardo Fibonacci did not actually invent or discover the Fibonacci sequence (which first appears in Indian mathematics in connection with Sanskirt prosody), but he used it as an example in his book, Liber Abaci, when studying the idealized population growth of rabbits.

Fibonacci sequences appear in biological settings - the branching in trees, the arrangement of leaves on a stem, the fruitlets of a pineapple, the flowering of artichoke, the uncurling of a fern, the arrangement of seeds in a pine cone, and much more.  

For more on the Fibonacci sequence in nature, click the collage!

Officially registered tartan graphics on this site courtesy of The Scottish Tartans Authority.  Other tartans from talented tartan artists may also be featured.

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