fact: Fixpoint enum_compn_rec aux n : (seq (seq nat)) := if aux is aux'.+1 then if n == 0 then [:: [::]] else flatten [seq [seq i :: p | p <- enum_compn_rec aux' (n - i) ] | i <- iota 1 n] else [:: [::]].
imports: HB(structures) mathcomp(all_ssreflect) tools combclass sorted partition subseq ordtype