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A271610
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Number of ways to reciprocally link elements of an n X n X n triangular array with themselves or a neighbor, with no more than 1 elements linked to themselves.
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1
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1, 3, 2, 6, 240, 2238, 2196, 37004, 20454036, 970623228, 2317631400, 216893681800, 1257138602103744, 316487245419538728, 2326335506123418128, 1208982377794384163088, 63184698521304672890081520, 85953148896748583125564477008, 2220650888749669503773432361504
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OFFSET
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1,2
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COMMENTS
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In other words, the number of maximum matchings in the (n-1)-triangular grid graph. - Eric W. Weisstein, Jun 14 2017
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LINKS
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Eric Weisstein's World of Mathematics, Matching
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FORMULA
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EXAMPLE
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All solutions for n=4
.....6........5........6........6........5........5
....5.1......2.6......5.1......6.1......2.5......2.6
...2.6.6....5.5.1....2.4.3....5.1.6....5.2.6....4.3.1
Element moves: 0=itself 1=nw 2=ne 3=w 4=e 5=sw 6=se, reciprocals total 7
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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