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 A276549 #11 Jun 16 2017 03:50:18
%S A276549 1,1,3,9,31,112,467,2141,10739,58454,340389,2110093,13830234,95475087,
%T A276549 691543059,5240282987,41432986587,341040306207,2916376237349,
%U A276549 25862097428262,237434959190586,2253358056942644,22076003468637449,222979436688500085,2319295172178428701
%N A276549 Number of primitive (aperiodic) reversible string structures with n beads using an infinite alphabet.
%H A276549 Andrew Howroyd, <a href="/A276549/b276549.txt">Table of n, a(n) for n = 1..200</a>
%F A276549 a(n) = Sum_{d|n} mu(n/d) * A103293(d+1).
%t A276549 b[n_] := SeriesCoefficient[Exp[(Exp[2*x] - 3)/2 + Exp[x]], {x, 0, n}]*n!;
%t A276549 c[n_] := If[n == 0, 1, (BellB[n - 1] + If[Mod[n, 2] == 1, b[(n - 1)/2], Sum[Binomial[n/2 - 1, k]*b[k], {k, 0, n/2 - 1}]])/2];
%t A276549 a[n_] := DivisorSum[n, MoebiusMu[n/#] c[# + 1]&];
%t A276549 Array[a, 25] (* _Jean-François Alcover_, Jun 16 2017, using _Alois P. Heinz_'s code for A103293 *)
%Y A276549 Row sums of A276544.
%Y A276549 Cf. A103293.
%K A276549 nonn
%O A276549 1,3
%A A276549 _Andrew Howroyd_, Apr 09 2017