Mathematics
The Ramanujan Tau Function and Modular Forms
Quick fact
The Ramanujan tau function, defined by the coefficients of the modular discriminant, satisfies surprising congruences such as τ(n) ≡ σ₁₁(n) mod 691, which were first observed by Ramanujan.
Why this is interesting
You've probably heard of prime numbers, but what about a sequence of numbers that hides secrets about primes and appears from a simple infinite product?