Alphanumeric Sequences

alnumseq.js

const f = (a, b) => [].concat(...a.map(d => b.map(e => [].concat(d, e))))
const cartesian = (a, b, ...c) => (b ? cartesian(f(a, b), ...c) : a)

const letters = Array.from({ length: 26 }, (k, v) => String.fromCharCode(v + 65))
const numbers = Array.from({ length: 9 }, (k, v) => v)

console.log(cartesian(letters, numbers))