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 A060296 #23 Jan 29 2025 07:08:56
%S A060296 1,1,-1,5,6,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
%T A060296 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
%U A060296 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3
%N A060296 Number of regular convex polytopes in n-dimensional space, or -1 if the number is infinite.
%D A060296 H. S. M. Coxeter, Regular Polytopes, 3rd ed., Dover, NY, 1973.
%D A060296 B. Grünbaum, Convex Polytopes. Wiley, NY, 1967, p. 424.
%D A060296 P. McMullen and E. Schulte, Abstract Regular Polytopes, Encyclopedia of Mathematics and its Applications, Vol. 92, Cambridge University Press, Cambridge, 2002.
%H A060296 John Baez, <a href="http://math.ucr.edu/home/baez/platonic.html">Platonic Solids in All Dimensions</a>, Nov 12 2006.
%H A060296 Brady Haran, Pete McPartlan, and Carlo Sequin, <a href="https://www.youtube.com/watch?v=2s4TqVAbfz4">Perfect Shapes in Higher Dimensions</a>, Numberphile video (2016)
%H A060296 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1).
%F A060296 a(n) = 3 for all n > 4. - _Christian Schroeder_, Nov 16 2015
%e A060296 a(2) = -1 because of the regular polygons in the plane.
%e A060296 a(3) = 5 because in R^3 the regular convex polytopes are the 5 Platonic solids.
%t A060296 PadRight[{1, 1, -1, 5, 6}, 100, 3] (* _Paolo Xausa_, Jan 29 2025 *)
%Y A060296 Cf. A000943, A000944, A053016, A063927, A093478, A093479.
%K A060296 sign,easy
%O A060296 0,4
%A A060296 Ahmed Fares (ahmedfares(AT)my-deja.com), Mar 24 2001