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 A278994 #15 Nov 03 2021 06:03:47 %S A278994 0,1,1,4,18,116,1060,13019,193425,3313522,63667788,1351700744, %T A278994 31390695708,791372281393,21523271532811,628166776833181, %U A278994 19582955637428422,649472761243051940,22833268501579122332,848230375982060558217 %N A278994 Number of simple chord diagrams with n chords, modulo all symmetries. %H A278994 E. Krasko and A. Omelchenko, <a href="http://arxiv.org/abs/1601.05073">Enumeration of Chord Diagrams without Loops and Parallel Chords</a>, arXiv preprint arXiv:1601.05073 [math.CO], 2016. %H A278994 E. Krasko and A. Omelchenko, <a href="https://doi.org/10.37236/6037">Enumeration of Chord Diagrams without Loops and Parallel Chords</a>, The Electronic Journal of Combinatorics, 24(3) (2017), #P3.43. %Y A278994 Cf. A003436, A003437, A007474, A278990, A278991, A278992, A278993. %K A278994 nonn %O A278994 1,4 %A A278994 _N. J. A. Sloane_, Dec 07 2016