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 A381366 #21 Mar 03 2025 13:33:06
%S A381366 3732480,253603223500400479331942400000,
%T A381366 66038535945066815418194228229716898861828197815802983951534337590785326501068800000000000000000
%N A381366 Number of possible configurations of an n dimensional Rubik's simplex.
%H A381366 Amiram Eldar, <a href="/A381366/b381366.txt">Table of n, a(n) for n = 3..7</a>
%H A381366 Giovanni Luca Marchetti, <a href="https://arxiv.org/abs/2502.13518">Rubik's Abstract Polytopes</a>, arXiv:2502.13518 [math.CO], 2025.
%F A381366 See formula (18) on p. 14 of Marchetti.
%t A381366 a[n_] := (1/(If[n >= 5, 1, 3] * 2^(3*n - 2))) * Product[(n-i)!^Binomial[n+1, i+1]*Binomial[n+1, i+1]!, {i, 0, n-2}]; Array[a, 3, 3] (* _Amiram Eldar_, Feb 21 2025 *)
%o A381366 (PARI) a(n) = my(c=1); if (n<5, c=3); prod(i=0, n-2, ((n-i)!)^binomial(n+1,i+1)*binomial(n+1,i+1)!)/(c*2^(3*n-2));
%Y A381366 Cf. A079746 (for a(3)=3732480), A381367.
%K A381366 nonn
%O A381366 3,1
%A A381366 _Michel Marcus_, Feb 21 2025