Monstrous moonshine: j-function coefficients as Monster irreducible dimensions (string-theory)

String-theory application of L0 modular-form and Euler-product. The Klein j-function j(τ) is the fundamental SL(2,ℤ)-invariant modular function on the upper half-plane, with q-expansion j(τ) = q^(−1) + 744 + 196884·q + 21493760·q² +…