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 A008447 #15 Jul 08 2025 01:04:09
%S A008447 1,56,420,896,2366,3360,6440,7168,14196,14168,22120,24192,37912,33824,
%T A008447 55440,50176,75838,71232,98700,88704,141960,117824,156520,150528,
%U A008447 217672,173656,261240,218624,303424,273504,355600,301056,455028,359744,474320
%N A008447 Theta series of A_7 lattice.
%D A008447 J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 110.
%t A008447 terms = 29; f[q_] = LatticeData["A7", "ThetaSeriesFunction"][-I Log[q]/Pi]; s = Series[f[q], {q, 0, 2 terms}]; DeleteCases[CoefficientList[s, q^(1/2) ] // Round, 0][[1 ;; terms]] (* _Jean-François Alcover_, Jul 04 2017 *)
%o A008447 (Magma) L:=Lattice("A",7); T1<q> := ThetaSeries(L,60);
%Y A008447 Cf. A023919 (dual).
%K A008447 nonn
%O A008447 0,2
%A A008447 _N. J. A. Sloane_
%E A008447 More terms from _Sean A. Irvine_, Jun 12 2019