A030270 Number of nonisomorphic and nonantiisomorphic reflexive transitive and cotransitive (complement is transitive) relations.

1, 1, 3, 5, 12, 24, 58, 128, 309, 717, 1731, 4109, 9920, 23780, 57410, 138192, 333625, 804457, 1942131, 4686341, 11313828, 27308256, 65927962, 159150320, 384222861, 927562581, 2239334163, 5406150125, 13051600952, 31509157004

Offset

0,3

Links

Michael De Vlieger, Table of n, a(n) for n = 0..2614

Stephan Mertens, Domination Polynomials of the Grid, the Cylinder, the Torus, and the King Graph, arXiv:2408.08053 [math.CO], 2024. See p. 21.

Formula

a(n) = (A001333(n) + A001333(floor((n+2)/2))) / 2.

Mathematica

Table[((-I)^n  ChebyshevT[n, I] + (-I)^#  ChebyshevT[#, I])/2 &[Floor[(n + 2)/2]], {n, 0, 29}] (* Michael De Vlieger, Aug 22 2024 *)

Crossrefs

Sequence in context: A186334 A303587 A151524 * A129757 A135019 A141685

Adjacent sequences: A030267 A030268 A030269 * A030271 A030272 A030273

Keyword

nonn,easy

Author

Christian G. Bower

Status

approved