1,2

The first four terms are not that difficult to verify. In fact, for n < 5 the subalgebra lattice of Re(n) is the dual of the subgroup lattice of S_n. Hence a(n) = A005432(n) for n < 5.

Relation algebras are closed under union, intersection, complement, composition, inverse, and identity.

Bjarni Jónsson, Maximal algebras of binary relations. In: Contributions to Group Theory, Contemporary Mathematics, vol. 33, pp. 299-307. Amer. Math. Soc., Providence (1984).

Cf. A005432.

Sequence in context: A036752 A065563 A035105 * A073969 A379724 A295863

Adjacent sequences: A386590 A386591 A386592 * A386594 A386595 A386596

nonn,hard,more

Jeremy F. Alm, Jul 26 2025

approved