A030270 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

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

(list; graph; refs; listen; history; text; internal format)

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