This Fibonacci joke is funnier than the last two combined!
The humor in this joke comes from how the Fibonacci sequence is created. That is, each number of the sequence comes from the sum of the previous two combined with the initial condition that the first two terms are 1 and 1. So 1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8, etc. making the sequence 1, 1, 2, 3, 5, 8, 13, 21, ... So this joke has the last two Fibonacci jokes posted here combined in one!
Fibonacci. Easy as 1, 1, 2, 3!
This Fibonacci cartoon has a lot going on. In the forefront, we have "Fibonacci. Easy as 1, 1, 2, 3!" which is a reference to the song "ABC easy as 123" and to the Fibonacci sequence itself of 1, 1, 2, 3. At the bottom, you can see a sequence of rabbits which represent Fibonacci's original development of the sequence. The sequence represents pairs of rabbit that are procreating (as rabbits do). See a bit more about the rabbit question here. At the top left, you can see the tracing of sunflower seeds following the golden ratio. The golden ratio is appears in the Fibonacci sequence by dividing a given term by the preceding term (such as 8/5 = 1.6, 13/8 = 1.625, 21/13 = 1.615, ... ~1.618). You can see an example of these golden spirals in the golden sunflower here. At the top right, you can see the golden spiral inside the golden rectangle, one way to geometrically represent the Fibonacci sequence. For a detailed description of the golden rectangle, see here.
How do mathematicians cheer? 2, 3, 5, 8! Who do we appreciate? Fibonacci!
Many know the common cheer: 2, 4, 6, 8! Who do we appreciate? [Insert team name here]. Instead of counting by twos, this joke relies on the Fibonacci sequence where each term is the sum of the previous two: 1, 1, 2, 3, 5, 8... Putting the new sequence into our cheer gives us the Mathematicians' Cheer!