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 A361955 #8 Apr 01 2023 15:48:53 %S A361955 1,1,1,3,10,42,202,1146,7493,56996,508609,5414635,70214227,1134439731, %T A361955 23331152887,621768153861,21761221300058,1009759125475973, %U A361955 62534859409597022,5193886959561972984,580677490292990902682,87649885799470898359728,17907726747155924589913398 %N A361955 Number of unlabeled connected weakly graded (ranked) posets with n elements. %C A361955 Here weakly graded means that there exists a rank function rk from the poset to the integers such that whenever v covers w in the poset, we have rk(v) = rk(w) + 1. %H A361955 Andrew Howroyd, <a href="/A361955/b361955.txt">Table of n, a(n) for n = 0..40</a> %H A361955 Wikipedia, <a href="https://en.wikipedia.org/wiki/Graded_poset">Graded poset</a>. %F A361955 Inverse Euler transform of A361920. %o A361955 (PARI) \\ See PARI link in A361953 for program code. %o A361955 A361955seq(20) %Y A361955 Row sums of A361954. %Y A361955 Cf. A000608, A361920, A361953. %K A361955 nonn %O A361955 0,4 %A A361955 _Andrew Howroyd_, Mar 31 2023