Proof of `Coproduct and shuffle identities` (4th statement)
groundedproofs/Lax825748Proofs/PermutationPairing.lean · lax-825748
What this proof establishes
Assuming the claims on the left, the claim on the right holds — checked by the archive's pipeline. Proof code is not displayed here.
Description
Expand the coproduct over assignments of Lie factors to tensor slots. Nonsurjective assignments vanish, and the bijective ones are permutations.