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 A173403 #27 Jan 16 2024 04:11:06
%S A173403 1,1,13,469,63577,33231721,68519123173,562469619451069,
%T A173403 18442242396353040817,2417685638793025070212561,
%U A173403 1267626422541873052658376446653,2658442047546208031914776455678477989,22300713297142388711251601783864453690641417
%N A173403 Inverse binomial transform of A002416.
%C A173403 a(n) is the number of n X n matrices of 0's and 1's with the property that there is no index k such that both the k-th column and the k-th row consist of all zeros.
%C A173403 a(n) is the number of binary relations on n labeled vertices with no vertex of indegree and outdegree = 0. - _Geoffrey Critzer_, Oct 02 2012
%D A173403 E. A. Bender and S. G. Williamson, Foundations of Combinatorics with Applications, Dover, 2005, exercise 4.1.6.
%H A173403 Brian Drake, <a href="/A173403/b173403.txt">Table of n, a(n) for n = 0..50</a>
%F A173403 a(n) = Sum_{k=0..n} (-1)^k*binomial(n,k)*2^((n-k)^2).
%F A173403 a(n) ~ 2^(n^2). - _Vaclav Kotesovec_, Oct 30 2017
%p A173403 N:=8: seq( sum(binomial(n,i)*2^((n-i)^2)*(-1)^(i), i=0..n), n=0..N);
%t A173403 Table[Sum[(-1)^k Binomial[n,k] 2^(n-k)^2,{k,0,n}],{n,0,20}] (* _Geoffrey Critzer_, Oct 02 2012 *)
%Y A173403 Cf. A002416, A135748, A287065, A048291.
%K A173403 nonn
%O A173403 0,3
%A A173403 _Brian Drake_, Feb 17 2010