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Search: id:A061705
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| A061705 |
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Number of matchings in the wheel graph with n spokes. |
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+0
2
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| 2, 5, 10, 19, 36, 66, 120, 215, 382, 673, 1178, 2050, 3550, 6121, 10514, 17999, 30720, 52290, 88788, 150427, 254342, 429245, 723190, 1216514, 2043386, 3427661, 5742490, 9609355, 16062492, 26821698, 44744688, 74576735, 124192270
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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G.f.: x(2+x-2x^2-2x^3)/(1-x-x^2)^2. a_n=(n+1)fibonacci(n)+ 2fibonacci(n-1); a_n=sqrt(5)((n+1)*(u^n-v^n)+2(u^(n-1)-v^(n-1)))/5, where u=(1+sqrt(5))/2, v=(1-sqrt(5))/2;
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EXAMPLE
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a(3)=10 because the matchings in a wheel graph with spokes OA, OB, and OC are the empty set, {AB}, {BC}, {CA}, {OA}, {OB}, {OC}, {OA, BC}, {OB, CA}, {OC, AB}.
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CROSSREFS
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Sequence in context: A024827 A104161 A065613 this_sequence A052944 A132736 A068035
Adjacent sequences: A061702 A061703 A061704 this_sequence A061706 A061707 A061708
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 18 2001
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