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 A008987 #53 Mar 30 2024 12:15:26 %S A008987 1,1,2,6,21,99,588,3829,27404,206543,1626638,13242275,110865868, %T A008987 950078474,8307074080,73908443799,667684486429 %N A008987 Number of immersions of an unoriented circle into the oriented sphere with n double points. %D A008987 V. I. Arnold, Topological Invariants of Plane Curves and Caustics, American Math. Soc., 1994, p. 18. %H A008987 R. Coquereaux and J.-B. Zuber, <a href="http://arxiv.org/abs/1507.03163">Maps, immersions and permutations</a>, arXiv preprint arXiv:1507.03163 [math.CO], 2015-2016. Also J. Knot Theory Ramifications 25, 1650047 (2016), DOI: <a href="https://doi.org/10.1142/S0218216516500474">10.1142/S0218216516500474</a>. %H A008987 Guy Valette, <a href="https://doi.org/10.1007/s40598-016-0049-3">A Classification of Spherical Curves Based on Gauss Diagrams</a>, Arnold Math J. (2016) 2:383-405. %o A008987 (Magma) // see A260848 %Y A008987 Cf. A008986, A008988, A008989. First line of triangle A260848. %K A008987 nonn,more %O A008987 0,3 %A A008987 _N. J. A. Sloane_ %E A008987 a(6)-a(7) from _Guy Valette_, Feb 09 2004 %E A008987 a(8)-a(9) from _Robert Coquereaux_ and Jean-Bernard Zuber, Jul 21 2015 %E A008987 a(10) from same source added by _N. J. A. Sloane_, Mar 03 2016 %E A008987 a(11)-a(14) from _Brendan McKay_, Mar 11 2023 %E A008987 a(15)-a(16) from _Brendan McKay_, Mar 29 2024