The Dixmier conjecture fails for the Weyl algebras An, n ≥ 3

We record the Weyl-algebra corollary of L. Alpoge's July 20, 2026 counterexample to the Jacobian Conjecture in dimension 3 (found using Claude Fable 5): an explicit injective, non-surjective endomorphism of the third Weyl algebra A_3(C), verified in exact arithmetic by the included script. Consequently the generalized Dixmier conjecture fails for A_n for every n >= 3, and the Poisson conjecture of Adjamagbo-van den Essen fails for n >= 3 as well. The note is self-contained: the counterexample's defining properties are re-verified independently, a short proof of non-surjectivity is included, and the surviving implication chain DC_2 => JC_2 => DC_1 is recorded. Dixmier's original problem, for A_1, remains open.