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.
a(2) = 24 since a 4D hypercube contains twenty-four faces.
a(2) = 32 since a 4D hypercube contains thirty-two edges.
a(1) = 24 because the mix of the tetrahedron {3,3} and the octahedron {3,4} has 24 vertices, 144 edges, 96 facets, and the size of the automorphism group (which is also the number of flags) is 576.
a(1) = 144 because the mix of the tetrahedron {3,3} and the octahedron {3,4} has 24 vertices, 144 edges, 96 facets, and the size of the automorphism group (which is also the number of flags) is 576.
The third number in the sequence is 36 because the third Platonic solid has eight faces and the pips on an eight-faced die add up to 36 [by sum_1^n(n) = 1/2 * n * (n+1), so 1/2 * 8 * 9 = 36 for n = 8].
# (# + 1)/2 & /@ {4, 6, 8, 12, 20} (* Robert G. Wilson v, Apr 18 2008 *)
for $n (4, 6, 8, 12, 20) { print $n*($n+1)/2 }
lista() = {ve = [6, 12, 12, 30, 30 ]; vf = [4, 6, 8, 12, 20 ]; for (i=1, 5, nb = vf[i]!/(2*ve[i]); print1(nb, ", "););} \\ Michel Marcus, Aug 25 2014
a(1) = 576 because the mix of the tetrahedron {3, 3} and the octahedron {3,4} has 24 vertices, 144 edges, 96 facets, and the size of the automorphism group (which is also the number of flags) is 576.
graph \ n-cycle | 3 4 5 6 7 8 9 10 11 12 13 ...
-------------------+-------------------------------------------------
tetrahedral graph | 4 3
cubical graph | 0 6 0 16 0 6
octahedral graph | 8 15 24 16
dodecahedral graph | 0 0 12 0 0 30 20 36 120 100 60 ...
icosahedral graph | 20 30 72 240 720 1620 2680 3336 2880 1280
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