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 A018225 #15 Feb 05 2019 14:01:39 %S A018225 1,1,2,6,31,255,2788,37333,578799,10134071,197394232,4231417728, %T A018225 98991987830,2510081238264,68583045013542,2009094843480565, %U A018225 62824038815664719,2088829704241946181,73591470349452760456,2738742863175749456078 %N A018225 Number of connected chord diagrams of degree n. %H A018225 Alexander Stoimenow, <a href="https://doi.org/10.1016/S0012-365X(99)00347-7">On the number of chord diagrams</a>, Discr. Math. 218 (2000), 209-233. %F A018225 a(n) = A007769(n) - A317184(n). - _Sean A. Irvine_, Feb 05 2019 %t A018225 Stoimenow states that a Mma package is available from his website. - _N. J. A. Sloane_, Jul 26 2018 %K A018225 nonn %O A018225 1,3 %A A018225 Alexander Stoimenow (stoimeno(AT)mail.informatik.hu-berlin.de) %E A018225 More terms from _Sean A. Irvine_, Feb 05 2019