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 A101370 #52 Mar 25 2025 02:48:37 %S A101370 1,4,24,196,2016,24976,361792,5997872,111969552,2324081728, %T A101370 53089540992,1323476327488,35752797376128,1040367629940352, %U A101370 32441861122796672,1079239231677587264,38151510015777089280,1428149538870997774080,56435732691153773665280 %N A101370 Number of zero-one matrices with n ones and no zero rows or columns. %C A101370 a(n) = (1/(4*n!)) * Sum_{r, s>=0} (r*s)_n / 2^(r+s), where (m)_n is the falling factorial m * (m-1) * ... * (m-n+1). [Maia and Mendez] %D A101370 Georg Cantor, Gesammelte Abhandlungen mathematischen und philosophischen Inhalts, p. 435 (IV, 4. Mitteilungen zur Lehre vom Transfiniten, VIII Nr. 13), Springer, Berlin. [_Rainer Rosenthal_, Apr 10 2007] %H A101370 Alois P. Heinz, <a href="/A101370/b101370.txt">Table of n, a(n) for n = 1..400</a> %H A101370 P. J. Cameron, D. A. Gewurz and F. Merola, <a href="http://www.maths.qmw.ac.uk/~pjc/preprints/product.pdf">Product action</a>, Discrete Math., 308 (2008), 386-394. %H A101370 Giulio Cerbai and Anders Claesson, <a href="https://arxiv.org/abs/2411.08426">Enumerative aspects of Caylerian polynomials</a>, arXiv:2411.08426 [math.CO], 2024. See pp. 3, 19. %H A101370 Loïc Foissy, Claudia Malvenuto, and Frédéric Patras, <a href="https://arxiv.org/abs/2503.14417">Matrix symmetric and quasi-symmetric functions and noncommutative representation theory</a>, arXiv:2503.14417 [math.CO], 2025. See p. 20. %H A101370 M. Maia and M. Mendez, <a href="https://arxiv.org/abs/math/0503436">On the arithmetic product of combinatorial species</a>, arXiv:math/0503436 [math.CO], 2005. %F A101370 a(n) = (Sum s(n, k) * P(k)^2)/n!, where P(n) is the number of labeled total preorders on {1, ..., n} (A000670), s are signed Stirling numbers of the first kind. %F A101370 G.f.: Sum_{m>=0,n>=0} Sum_{j=0..n} (-1)^(n-j)*binomial(n,j)*((1+x)^j-1)^m. - _Vladeta Jovovic_, Mar 25 2006 %F A101370 Inverse binomial transform of A007322. - _Vladeta Jovovic_, Aug 17 2006 %F A101370 G.f.: Sum_{n>=0} 1/(2-(1+x)^n)/2^(n+1). - _Vladeta Jovovic_, Sep 23 2006 %F A101370 G.f.: Sum_{n>=0} A000670(n)^2*log(1+x)^n/n! where 1/(1-x) = Sum_{n>=0} A000670(n)*log(1+x)^n/n!. - _Paul D. Hanna_, Nov 07 2009 %F A101370 a(n) ~ n! / (2^(2+log(2)/2) * (log(2))^(2*(n+1))). - _Vaclav Kotesovec_, Dec 31 2013 %e A101370 a(2)=4: %e A101370 [1 1] [1] [1 0] [0 1] %e A101370 ..... [1] [0 1] [1 0] %e A101370 From _Gus Wiseman_, Nov 14 2018: (Start) %e A101370 The a(3) = 24 matrices: %e A101370 [111] %e A101370 . %e A101370 [11][11][110][101][10][100][011][01][010][001] %e A101370 [10][01][001][010][11][011][100][11][101][110] %e A101370 . %e A101370 [1][10][10][10][100][100][01][01][010][01][010][001][001] %e A101370 [1][10][01][01][010][001][10][10][100][01][001][100][010] %e A101370 [1][01][10][01][001][010][10][01][001][10][100][010][100] %e A101370 (End) %t A101370 m = 17; a670[n_] = Sum[ StirlingS2[n, k]*k!, {k, 0, n}]; Rest[ CoefficientList[ Series[ Sum[ a670[n]^2*(Log[1 + x]^n/n!), {n, 0, m}], {x, 0, m}], x]] (* _Jean-François Alcover_, Sep 02 2011, after g.f. *) %t A101370 Table[Length[Select[Subsets[Tuples[Range[n],2],{n}],And[Union[First/@#]==Range[Max@@First/@#],Union[Last/@#]==Range[Max@@Last/@#]]&]],{n,5}] (* _Gus Wiseman_, Nov 14 2018 *) %o A101370 (GAP) P:=function(n) return Sum([1..n],x->Stirling2(n,x)*Factorial(x)); end; %o A101370 (GAP) F:=function(n) return Sum([1..n],x->(-1)^(n-x)*Stirling1(n,x)*P(x)^2)/Factorial(n); end; %o A101370 (PARI) {A000670(n)=sum(k=0,n,stirling(n, k,2)*k!)} %o A101370 {a(n)=polcoeff(sum(m=0,n,A000670(m)^2*log(1+x+x*O(x^n))^m/m!),n)} %o A101370 /* _Paul D. Hanna_, Nov 07 2009 */ %Y A101370 Cf. A000670 (the sequence P(n)), A049311 (row and column permutations allowed), A120733, A122725, A135589, A283877, A321446, A321587. %K A101370 easy,nonn %O A101370 1,2 %A A101370 _Peter J. Cameron_, Jan 14 2005