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A302719 Number of edge covers in the n-path complement graph. 1

%I

%S 0,0,0,2,26,580,23116,1703182,237842582,64143512608,33852316389688,

%T 35268292090882874,72930742736413804146,300323342846133370497564,

%U 2467442527810798875863471748,40490661363717159406441954638982,1327931037076594186049396631983031214

%N Number of edge covers in the n-path complement graph.

%H Andrew Howroyd, <a href="/A302719/b302719.txt">Table of n, a(n) for n = 1..50</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/EdgeCover.html">Edge Cover</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PathComplementGraph.html">Path Complement Graph</a>

%F a(n) = Sum_{i=0..n} (Sum_{k=0, n-i} binomial(n-i, k)*A006129(k)*(2^i)^k*(2^i-1)^(n-i-k)) * (Sum_{j=floor(i/2}, i} (-1)^j*binomial(n-j, i-j)*binomial(j-1, 2*j-i)*2^binomial(i, 2)/2^j). - _Andrew Howroyd_, Apr 23 2018

%t Table[Sum[Sum[Binomial[n - i, k] Sum[(-1)^(k - j) Binomial[k, j] 2^Binomial[j, 2], {j, 0, k}] (2^i)^k If[i == 0 && k == n, 1, (2^i - 1)^(n - i - k)], {k, 0, n - i}] Sum[(-1)^j Binomial[n - j, i - j] Binomial[j - 1, 2 j - i] 2^(Binomial[i, 2] - j), {j, Ceiling[i/2], i}], {i, 0, n}], {n, 10}] (* _Eric W. Weisstein_, Apr 24 2018 *)

%o (PARI)

%o a(n)={ my(p=serlaplace(sum(k=0, n, 2^binomial(k,2)*x^k/k!)/exp(x+O(x*x^n))));

%o sum(i=0, n, sum(k=0, n-i, binomial(n-i,k)*polcoeff(p,k)*(2^i)^k*(2^i-1)^(n-i-k)) * sum(j=i\2, i, (-1)^j * binomial(n-j, i-j) * binomial(j-1, 2*j-i) * 2^binomial(i,2)/2^j))} \\ _Andrew Howroyd_, Apr 23 2018

%Y Cf. A006129, A170941.

%K nonn

%O 1,4

%A _Eric W. Weisstein_, Apr 12 2018

%E Terms a(10) and beyond from _Andrew Howroyd_, Apr 23 2018

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Last modified December 11 21:21 EST 2019. Contains 329937 sequences. (Running on oeis4.)