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 A086206 #21 Apr 14 2023 08:21:30
%S A086206 0,1,27,2401,759375,887503681,3938980639167,67675234241018881,
%T A086206 4558916353692287109375,1213972926354344043087129601,
%U A086206 1284197945649659948122178573052927,5412701932445852698371002894178179850241,91054366938067173656011584805755385081787109375
%N A086206 Number of n X n matrices with entries in {0,1} with no zero row and with zero main diagonal.
%C A086206 Equivalently a(n) is the number of labeled digraphs on [n] with no out-nodes. Cf. A362013. - _Geoffrey Critzer_, Apr 13 2023
%H A086206 Andrew Howroyd, <a href="/A086206/b086206.txt">Table of n, a(n) for n = 1..50</a>
%F A086206 a(n) = (2^(n-1)-1)^n = Sum_{k=0..n} (-1)^k*binomial(n, k)*2^((n-k)*(n-1)).
%F A086206 a(n) = A092477(n, n-1).
%F A086206 Sum_{n>=0} a(n)*x^n/A011266(n) = (Sum_{n>=0} (-x)^n/A011266(n))*(Sum_{n>=0} 2^(n(n-1))*x^n/A011266(n)). - _Geoffrey Critzer_, Apr 13 2023
%o A086206 (PARI) a(n) = {(2^(n-1)-1)^n} \\ _Andrew Howroyd_, Jan 05 2020
%Y A086206 Cf. A055601, A086193, A092477, A362013.
%K A086206 easy,nonn
%O A086206 1,3
%A A086206 _Vladeta Jovovic_, Aug 27 2003
%E A086206 Terms a(11) and beyond from _Andrew Howroyd_, Jan 05 2020