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 A129421 #16 Jun 02 2025 16:31:59
%S A129421 0,1,1,6,15,120,933,13303,252207,6450828,205475039,7936493756,
%T A129421 363639228194,19476976825809,1205115679461426,85288127619421544,
%U A129421 6845235025444882069,618411485467843477405,62471139399366989007575,7014991719815977343879171
%N A129421 Number of isomorphism classes of connected 6-regular loopless multigraphs of order n.
%C A129421 Initial terms computed using software at http://users.cecs.anu.edu.au/~bdm/nauty/
%H A129421 Brendan McKay and Adolfo Piperno, <a href="http://pallini.di.uniroma1.it">Nauty and Traces</a>
%F A129421 Inverse Euler transform of A129422. - _Andrew Howroyd_, Mar 17 2020
%o A129421 (nauty) geng -c -d1 ${n} -q | multig -r6 -u # _Natan Arie Consigli_, Jun 05 2017
%Y A129421 Column k=6 of A328682.
%Y A129421 Cf. A129422, A129432, A000421, A129417, A129419, A129423, A129425, A328682.
%K A129421 nonn
%O A129421 1,4
%A A129421 _Brendan McKay_, Apr 15 2007
%E A129421 a(1)=0 prepended and a(14)-a(20) from _Andrew Howroyd_, Mar 17 2020