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 A318129 #11 Jun 19 2025 08:31:17
%S A318129 1,1,3,91,31827,2147158387,9223372011085950171,
%T A318129 170141183460469231602560095290109272523,
%U A318129 57896044618658097711785492504343953923912733397452774312538303978325772978595
%N A318129 Number of sets of nonempty subsets of {1,...,n} with intersection {}.
%F A318129 Binomial transform of A318128.
%F A318129 a(n) = A318130(n) - 2^(2^n - 1). [corrected]
%e A318129 The a(2) = 3 sets of sets are {}, {{1},{2}}, {{1},{2},{1,2}}.
%t A318129 Table[Length[Select[Subsets[Rest[Subsets[Range[n]]]],Or[#=={},Intersection@@#=={}]&]],{n,0,4}]
%Y A318129 Cf. A000371, A001146, A003465,A040996, A119563, A131288.
%Y A318129 Cf. A318128, A318130, A318131, A318132.
%K A318129 nonn
%O A318129 0,3
%A A318129 _Gus Wiseman_, Aug 18 2018