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A308155
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Number of (undirected) cycles in the n-Hanoi graph.
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1
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OFFSET
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1,2
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COMMENTS
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a(7) has 266 decimal digits and a(8) has 796 decimal digits. - Andrew Howroyd, Sep 10 2019
Also the number of chordless cycles in the (n+1)-Hanoi graph. - Eric W. Weisstein, May 23 2023
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LINKS
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FORMULA
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MATHEMATICA
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a[0] = 1; a[n_] := a[n] = a[n - 1]^2 (a[n - 1] + 1); Table[Sum[3^(n - k) a[k - 1]^3, {k, n}], {n, 6}] (* Eric W. Weisstein, May 23 2023 *)
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PROG
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(PARI) a(n)={my(s=1, d=1); for(i=2, n, d=d^2+d^3; s = 3*s + d^3); s} \\ Andrew Howroyd, Sep 10 2019
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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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