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A323499
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Number of minimum dominating sets in the n-triangular (Johnson) graph.
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1
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1, 3, 15, 15, 195, 105, 2625, 945, 38745, 10395, 634095, 135135, 11486475, 2027025, 229053825, 34459425, 4996616625, 654729075, 118505962575, 13749310575, 3038597637075, 316234143225, 83802047954625, 7905853580625, 2474532170735625, 213458046676875
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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2,2
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LINKS
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Andrew Howroyd, Table of n, a(n) for n = 2..200
Eric Weisstein's World of Mathematics, Johnson Graph
Eric Weisstein's World of Mathematics, Minimum Dominating Set
Eric Weisstein's World of Mathematics, Triangular Graph
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FORMULA
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a(n) = n!! for n odd.
a(n) = (n-1)!!*(1 + n*(n/2 - 1)) for n even. - Andrew Howroyd, Sep 08 2019
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PROG
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(PARI) a(n)={my(m=(n+1)\2); ((2*m)!/(m!*2^m))*if(n%2, 1, 1 + n*(n/2-1))} \\ Andrew Howroyd, Sep 08 2019
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CROSSREFS
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Cf. A290716, A290847, A298104, A303048, A303227, A304561.
Sequence in context: A237628 A074043 A120467 * A332961 A012634 A043060
Adjacent sequences: A323496 A323497 A323498 * A323500 A323501 A323502
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KEYWORD
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nonn
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AUTHOR
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Eric W. Weisstein, Jan 16 2019
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EXTENSIONS
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Terms a(14) and beyond from Andrew Howroyd, Sep 08 2019
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STATUS
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approved
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