This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A355047 #7 Jul 26 2022 13:56:41
%S A355047 3,26,198,1095,5259,22678,91887,354442,1320089,4780355,16943165,
%T A355047 59007970,202599228,687342673,2308586154,7687335917,25407923029,
%U A355047 83430814454,272382655862,884706011664,2860304423466,9208948000393
%N A355047 Number of oriented orthoplex n-ominoes with cell centers determining n-3 space.
%C A355047 Orthoplex polyominoes are connected sets of cells of regular tilings with Schläfli symbols {}, {4}, {3,4}, {3,3,4}, {3,3,3,4}, etc. These are tilings of regular orthoplexes projected on their circumspheres. Orthoplex polyominoes are equivalent to multidimensional polyominoes that do not extend more than two units along any axis, i.e., fit within a 2^d cube. This sequence is obtained using the first formula below. For oriented polyominoes, chiral pairs are counted as two.
%F A355047 a(n) = A355048(n) + A355049(n) = 2*A355048(n) - A355050(n) = 2*A355049(n) + A355050(n).
%e A355047 a(6)=3 because there are 3 hexominoes in 2^3 space, all achiral. The two vacant cells share just a face, an edge, or a vertex.
%Y A355047 Cf. A355048 (unoriented), A355049 (chiral), A355050 (achiral) A355051 (asymmetric), A355052 (multidimensional).
%K A355047 easy,nonn
%O A355047 6,1
%A A355047 _Robert A. Russell_, Jun 16 2022