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 A355998 #6 Jul 26 2022 13:58:50
%S A355998 1,48,1728,62720,2457600,105815808,5017600000,261227298816,
%T A355998 14860167413760,918839084134400,61439672177393700,4421589120000000000,
%U A355998 340976534987475000000,28064307240230900000000,2456376885785930000000000
%N A355998 Number of fixed orthoplex n-ominoes with cell centers determining (n-2)-space.
%C A355998 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. Two fixed polyominoes are identical only if one is a translation of the other.
%F A355998 a(n) = 2^(n-3) * n^(n-5) * (n-2) * (n-3)^2.
%F A355998 a(n) ~ A171860(n) / 2.
%e A355998 For A(4)=1, all 4 squares of the 2^2 space are used.
%t A355998 Table[2^(n-3) n^(n-5) (n-2) (n-3)^2, {n,4,30}]
%Y A355998 Cf. A171860 (multidimensional), A036367 (unoriented), A036368 (chiral), A036369 (asymmetric).
%Y A355998 Diagonal 2 of A355997.
%K A355998 nonn
%O A355998 4,2
%A A355998 _Robert A. Russell_, Jul 22 2022