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 A274974 #38 Nov 03 2017 09:48:58
%S A274974 1,13,49,117,225,381,593,869,1217,1645,2161,2773,3489,4317,5265,6341,
%T A274974 7553,8909,10417,12085,13921,15933,18129,20517,23105,25901,28913,
%U A274974 32149,35617,39325,43281,47493,51969,56717,61745,67061,72673,78589,84817,91365,98241
%N A274974 Centered octahemioctahedral numbers: a(n) = (4*n^3+24*n^2+8*n+3)/3.
%C A274974 Related to a faceting of the cuboctahedron, sharing the same triangular faces. The octahemioctahedron has the same edge and vertex arrangement as the cuboctahedron (as does A274973). Beginning with the third term, the six square faces are each now "missing" a square pyramid of size 1, 5, 14, 30, 55, 91...(A000330). See A274973 centered cubohemioctahedron for similar cuboctahedral faceting but without the triangular faces.
%H A274974 Steven Beard, <a href="https://oeis.org/w/images/c/c5/A274974_Beard.mp3">Music track made with this sequence</a>
%H A274974 Wikipedia, <a href="https://en.wikipedia.org/wiki/Octahemioctahedron">Octahemioctahedron</a>
%F A274974 a(n) = (4*n^3+24*n^2+8*n+3)/3.
%F A274974 G.f.: (-5*x^3+3*x^2+9*x+1)/(x-1)^4.
%t A274974 CoefficientList[Series[(-5 x^3 + 3 x^2 + 9 x + 1)/(x - 1)^4, {x, 0, 40}], x] (* or *)
%t A274974 Table[(4 n^3 + 24 n^2 + 8 n+3)/3, {n, 41}] (* _Michael De Vlieger_, Jul 13 2016 *)
%o A274974 (PARI) a(n)=(4*n^3+24*n^2+8*n+3)/3 \\ _Charles R Greathouse IV_, Nov 03 2017
%Y A274974 Cf. A005902 (centered cuboctahedral numbers), A274973 (centered cubohemioctahedral numbers).
%K A274974 nonn,easy
%O A274974 0,2
%A A274974 _Steven Beard_, Jul 13 2016