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 A179100 #11 Aug 04 2019 18:59:31
%S A179100 5,9,69,407,2997,22005,169389,1325889,10573677,85386881,697013325,
%T A179100 5739021051,47599593941,397234035333,3332690347437,28089543969855,
%U A179100 237711099004461,2018856328439841,17200553934626253,146966002696538271
%N A179100 a(n) = (1/n) * Sum_{k=0..n-1} (8k+5) T_k^2, where T_0, T_1, ... are central trinomial coefficients given by A002426.
%C A179100 On Jun 17 2010, _Zhi-Wei Sun_ conjectured that a(n) is an integer for every n=1,2,3,... and that a(p) == 3(p/3) (mod p) for any prime p, where (p/3) is the Legendre symbol. He also observed that Sum_{k=0..n-1} (2k+1) T_k*3^{n-1-k} = n * Sum_{k=0..n-1} C(n-1,k)*(-1)^(n-1-k)*(k+1)*C(2k,k).
%H A179100 Zhi-Wei Sun, <a href="http://arxiv.org/abs/1006.2776">Arithmetic properties of Apery numbers and central Delannoy numbers</a>, preprint, arXiv:1006.2776 [math.NT], 2010-2011.
%e A179100 For n=3 we have a(3) = (5*T_0^2 + 13*T_1^2 + 21*T_2^2)/3 = (5 + 13 + 21*9)/3 = 69.
%t A179100 TT[n_]:=Sum[Binomial[n,2k]Binomial[2k,k],{k,0,Floor[n/2]}] SS[n_]:=Sum[(8k+5)*TT[k]^2,{k,0,n-1}]/n Table[SS[n],{n,1,50}]
%Y A179100 Cf. A002426, A179089, A178808, A178790, A178791, A173774.
%K A179100 nonn
%O A179100 1,1
%A A179100 _Zhi-Wei Sun_, Jun 29 2010