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 A305005 #10 Jun 16 2018 13:42:13 %S A305005 1,1,2,9,111,6829,7783192,2414627236071,56130437209370100252463 %N A305005 Number of labeled clutters (connected antichains) spanning some subset of {1,...,n} without singleton edges. %H A305005 Gus Wiseman, <a href="/A048143/a048143_4.txt">Sequences enumerating clutters, antichains, hypertrees, and hyperforests, organized by labeling, spanning, and allowance of singletons</a>. %F A305005 Binomial transform of A048143 if we assume A048143(1) = 0. %F A305005 a(n) = A198085(n) - n + 1. - _Gus Wiseman_, Jun 11 2018 %e A305005 The a(3) = 9 clutters: %e A305005 {} %e A305005 {{1,2}} %e A305005 {{1,3}} %e A305005 {{2,3}} %e A305005 {{1,2,3}} %e A305005 {{1,2},{1,3}} %e A305005 {{1,2},{2,3}} %e A305005 {{1,3},{2,3}} %e A305005 {{1,2},{1,3},{2,3}} %Y A305005 Cf. A048143, A198085, A261006, A304912, A304981, A304982, A304983, A304984, A304985, A304986. %K A305005 nonn %O A305005 0,3 %A A305005 _Gus Wiseman_, May 23 2018