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 A266561 #15 Jan 28 2025 10:51:57
%S A266561 1,14,104,546,2275,8008,24752,68952,176358,419900,940576,1998724,
%T A266561 4056234,7904456,14858000,27041560,47805615,82317690,138389160,
%U A266561 227613750,366913365,580610160,903171360,1382805840,2086129500,3104160696,4559958144,6618272584
%N A266561 12-dimensional square numbers.
%C A266561 2*a(n) is number of ways to place 11 queens on an (n+11) X (n+11) chessboard so that they diagonally attack each other exactly 55 times. The maximal possible attack number, p=binomial(k,2)=55 for k=11 queens, is achievable only when all queens are on the same diagonal. In graph-theory representation they thus form the corresponding complete graph.
%H A266561 Feihu Liu, Guoce Xin, and Chen Zhang, <a href="https://arxiv.org/abs/2412.18744">Ehrhart Polynomials of Order Polytopes: Interpreting Combinatorial Sequences on the OEIS</a>, arXiv:2412.18744 [math.CO], 2024. See p. 15.
%H A266561 OEIS Wiki, <a href="https://oeis.org/wiki/Square_hyperpyramidal_numbers">Square hyperpyramidal numbers</a>, line d=12 of first table.
%F A266561 a(n) = binomial(n+11,11)*(n+6)/6.
%F A266561 a(n) = 2*binomial(n+12,12) - binomial(n+11,11).
%F A266561 a(n) = binomial(n+11,11) + 2*binomial(n+11,12) for n>0.
%F A266561 G.f.: (1+x)/(1-x)^13. - _Vincenzo Librandi_, Jan 01 2016
%t A266561 CoefficientList[Series[(1 + x)/(1 - x)^13, {x, 0, 33}], x] (* _Vincenzo Librandi_, Jan 01 2016 *)
%o A266561 (Magma) [Binomial(n+11,11)*(n+6)/6: n in [0..40]]; // _Vincenzo Librandi_, Jan 01 2016
%Y A266561 Cf. A000330, A002415, A005585, A040977, A050486, A053347, A054333, A054334, A057788.
%K A266561 nonn,easy
%O A266561 0,2
%A A266561 _Antal Pinter_, Dec 31 2015