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 A281456 #6 Jan 24 2017 09:59:03
%S A281456 1,0,0,0,1,0,0,0,0,0,0,1,0,0,0,1,0,0,1,0,0,0,1,0,0,1,0,0,0,2,0,0,1,1,
%T A281456 0,0,2,0,0,1,1,0,0,3,0,0,1,2,0,0,3,0,0,1,3,0,0,4,1,0,1,4,0,0,4,1,0,1,
%U A281456 5,0,0,5,2,0,1,7,0,0,5,3,0,1,8,0,0,6,5
%N A281456 Expansion of Product_{k>=1} (1 + x^(7*k-3)).
%H A281456 Vaclav Kotesovec, <a href="/A281456/b281456.txt">Table of n, a(n) for n = 0..10000</a>
%F A281456 a(n) ~ exp(sqrt(n/21)*Pi) / (2^(11/7)*21^(1/4)*n^(3/4)) * (1 - (3*sqrt(21)/(8*Pi) + 23*Pi/(336*sqrt(21))) / sqrt(n)). - _Vaclav Kotesovec_, Jan 22 2017, extended Jan 24 2017
%t A281456 nmax = 100; CoefficientList[Series[Product[(1 + x^(7*k - 3)), {k, 1, nmax}], {x, 0, nmax}], x]
%t A281456 nmax = 100; poly = ConstantArray[0, nmax + 1]; poly[[1]] = 1; poly[[2]] = 0; Do[If[Mod[k, 7] == 4, Do[poly[[j + 1]] += poly[[j - k + 1]], {j, nmax, k, -1}]; ], {k, 2, nmax}]; poly
%Y A281456 Cf. A109706, A281245, A281455, A281457, A281458, A280457.
%K A281456 nonn
%O A281456 0,30
%A A281456 _Vaclav Kotesovec_, Jan 22 2017