数楽

"Math Fun" is an interactive Android app that lets you intuitively experience the fascination of mathematics.

It includes 12 mathematical themes, allowing you to visually explore the fascinating properties of numbers through animations and charts. The HOME screen is divided into four categories (Prime Numbers and Divisors / The Magic of Digits / The Mystery of Repetition / Sequences and Geometry) using horizontal tabs, allowing you to naturally navigate through areas of interest. From those who struggle with math to number theory enthusiasts, everyone can enjoy the beauty of numbers.

[Included Themes]

■ Kaprekar Numbers
Experience the fascinating phenomenon where repeatedly rearranging and subtracting 3-digit and 4-digit numbers always converges to a specific constant (495 / 6174) through step-by-step animation.

■ Collatz Sequence
An unsolved problem where "even numbers are divided by 2, and odd numbers are multiplied by 3 + 1" is repeated. Visualize the sequence's trajectory with charts and observe how the number reaches 1.


■ Perfect Numbers & Amicable Numbers
6, 28, 496... Determine and search for perfect numbers whose sum of divisors is equal to itself. Furthermore, you can search for pairs of amicable numbers whose sum of divisors is equal to that of the other number.

■ Prime Numbers
In addition to primality testing and prime factorization, generate a list of prime numbers using the Sieve of Eratosthenes. Explore the profound world of prime numbers, including twin primes and Mersenne primes.

■ Fibonacci Sequence
0, 1, 1, 2, 3, 5, 8, 13... A beautiful sequence found in nature. Calculate the Nth term, determine the Fibonacci sequence, and display a sequence graph.

■ Harshad Numbers
Harshad numbers are numbers divisible by the sum of their digits. Discover the properties of these numbers hidden in everyday life through determination and list display.

■ Magic Square
Automatically generates a mystical number arrangement by placing numbers from 1 to N² in an N×N grid, where the sum of all rows, columns, and diagonals is equal. Experience the beauty of the magic square with an animation where cells appear one by one.

■ Goldbach's Conjecture
Verifies the unsolved conjecture that "all even numbers greater than or equal to 4 can be expressed as the sum of two prime numbers." You can decompose even numbers into prime number pairs and view a list of the decomposition numbers.

■ Smith Numbers
Composite numbers where the sum of each digit is equal to the sum of the digits of the prime factors obtained by prime factorization. For example, 22 = 2×11 → sum of digits 2+2=4, sum of prime factors 2+1+1=4. Explore the profound properties of these numbers with judgment and list display.

■ Lucky Numbers
"Lucky numbers" are numbers where the sum of the squares of each digit is repeatedly calculated until it reaches 1. For example, 19 → 1² + 9² = 82 → 8² + 2² = 68 → … → 1. You can observe the process of the number converging to 1 by following the calculation steps.

■ Palindromic Numbers
Determines numbers that read the same forwards and backwards (e.g., 121, 1331, 12321). Furthermore, in "Reverse Addition" mode, the operation of reversing and adding numbers is repeated, and the process of reaching a palindrome is animated in up to 30 steps. You can also search for "Ricrel number candidates" such as 196, which never reach a palindrome no matter how many times you repeat the process.

■ Pythagorean Triples 【NEW】
Determines triplets of integers that satisfy a² + b² = c² (e.g., (3, 4, 5), (5, 12, 13)) and visualizes the resulting right triangles with a gradient. It also determines whether they are "primitive Pythagorean triples" whose greatest common divisor is 1. In list mode, you can generate all primitive triplets below a specified upper limit based on Euclid's formula.

[Features]
- Categorized into 4 categories using horizontal tabs on the HOME screen
- Modern UI based on Material 3 design
- Dark mode / Light mode switching support (saved independently of system settings)
- Japanese / English bilingual support
- Smooth background processing of heavy calculations with coroutines
- Comfortable navigation of 12 themes with horizontally scrolling bottom tabs
- Compatible with both smartphones and tablets

Experience the "movement" and "beauty" of numbers that you can't find in math textbooks.