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A005033
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Number of nonequivalent dissections of a polygon into n quadrilaterals by nonintersecting diagonals rooted at a cell up to rotation.
(Formerly M3921)
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3
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1, 1, 5, 22, 116, 612, 3399, 19228, 111041, 650325, 3856892, 23107896, 139672312, 850624376, 5214734547, 32154708216, 199292232035, 1240877862315, 7758138260565, 48685766617950, 306558216362064, 1936246229757840, 12263985131919300, 77880114240872112
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OFFSET
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1,3
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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MATHEMATICA
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u[n_, k_, r_] := r*Binomial[(k-1)*n + r, n]/((k-1)*n + r);
T[n_, k_] := DivisorSum[GCD[n-1, k], EulerPhi[#]*u[(n-1)/#, k, k/#]&]/k;
a[n_] := T[n, 4];
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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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