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 A086193 Number of n X n matrices with entries in {0,1} with no zero row, no zero column and with zero main diagonal. 5
 1, 0, 1, 18, 1699, 592260, 754179301, 3562635108438, 63770601591579079, 4405870283636411477640, 1190873924687350003735546441, 1270602397076493907445608866890778, 5381240610642043789096251476993474339179 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Also the number of simple labeled digraphs on n nodes for which every vertex has indegree at least one and outdegree at least one. Also the number of edge covers on the n-crown graph. - Eric W. Weisstein, May 19 2017 LINKS Andrew Howroyd, Table of n, a(n) for n = 0..50 R. W. Robinson. Counting digraphs with restrictions on the strong components, (1996). W(n). Eric Weisstein's World of Mathematics, Crown Graph Eric Weisstein's World of Mathematics, Edge Cover FORMULA a(n) = Sum_{r=0..n} (-1)^(n-r)*binomial(n, r)*(2^(r-1)-1)^r*(2^r-1)^(n-r). - Vladeta Jovovic, Aug 27 2003 a(n) = sum( f(n, r), r=0..n ) where f(n, r) = binomial(n, r) (-1)^r (1-2^(-n+r+1))^(n-r) (1-2^(-n+r))^r 2^((n-r)(n-1)). - Brendan McKay, Aug 27 2003 E.g.f.: Sum_{k>=0} (2^(n-1)-1)^n*exp((1-2^n)*x)*x^n/n!. - Vladeta Jovovic, Feb 23 2008 a(n) ~ 2^(n*(n-1)). - Vaclav Kotesovec, May 04 2015 MATHEMATICA Table[ it = (Partition[ #1, n ] &) /@ IntegerDigits[ Range[ 0, -1 + 2^n^2 ], 2, n^2 ]; Count[ it, (q_)?MatrixQ /; Tr[ q ] === 0 && (Times @@ (Plus @@@ q)) > 0 && (Times @@ (Plus @@@ Transpose[ q ]) > 0) ], {n, 1, 4} ] (* Wouter Meeussen, Aug 25 2003 *) Table[Sum[(-1)^(n-r)*Binomial[n, r]*(2^(r-1)-1)^r*(2^r-1)^(n-r), {r, 0, n}], {n, 1, 15}] (* Vaclav Kotesovec, May 04 2015 after Vladeta Jovovic *) PROG (PARI) a(n)={sum(r=0, n, (-1)^(n-r)*binomial(n, r)*(2^(r-1)-1)^r*(2^r-1)^(n-r))} \\ Andrew Howroyd, Sep 09 2018 CROSSREFS Cf. A048291. Sequence in context: A003030 A276016 A086366 * A064347 A253121 A067303 Adjacent sequences:  A086190 A086191 A086192 * A086194 A086195 A086196 KEYWORD nonn AUTHOR W. Edwin Clark, Aug 25 2003 EXTENSIONS More terms from Brendan McKay, Aug 27 2003 a(0)=1 prepended by Andrew Howroyd, Sep 09 2018 STATUS approved

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Last modified October 18 14:52 EDT 2019. Contains 328161 sequences. (Running on oeis4.)