A number theory problem by Kaleem Kħặŋ

Which of the smallest Fibonacci number greater than 1 and is also a perfect square?

144 36 81 121

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3 solutions

The Fibonacci numbers are the numbers in the following integer sequence, called the Fibonacci sequence, and characterized by the fact that every number after the first two is the sum of the two preceding ones:

1 , 1 , 2 , 3 , 5 , 8 , 13 , 21 , 34 , 55 , 89 , 1,1,2,3,5,8,13,21,34,55,89, 144 \color{#D61F06}\boxed{144} , 233 , 377 , 610... ,233,377,610 ...

From the above, the smallest number greater than 1 1 which is a perfect square is 144 144 .

Áron Bán-Szabó
Jul 15, 2017

It is easy to find the smallest perfect square between the Fibonacci numbers:

Fibonacci Numbers:

1 , 1 , 2 , 3 , 5 , 8 , 13 , 21 , 34 , 55 , 89 , 144 , 233 , 1,1,2,3,5,8,13,21,34,55,89,\boxed{144},233,\cdots

Perfect squares:

1 , 4 , 9 , 16 , 25 , 36 , 49 , 64 , 81 , 100 , 121 , 144 , 169 , 1,4,9,16,25,36,49,64,81,100,121,\boxed{144},169,\cdots

When we want to find the smallest Fibonacci square, it's easy enough to list them out and check. How would we find the largest Fibonacci square? Is there a largest?

Zach Abueg - 3 years, 10 months ago
Vijay Simha
Dec 15, 2018

It is just a matter of inspecting Fibonacci numbers.

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233

and picking out a square from these.

144 is12^2

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