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A001660
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Hypotenusal numbers.
(Formerly M1706 N0675)
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1
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1, 1, 2, 6, 36, 876, 408696, 83762796636, 3508125906207095591916, 6153473687096578758445014683368786661634996, 18932619208894981833333582059033329370801260096062214926751788496235698477988081702676
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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REFERENCES
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N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
J. J. Sylvester and M. J. Hammond, On Hamilton's numbers, Phil. Trans. Roy. Soc., 178 (1887), 285-312.
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LINKS
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E. Lucas, Théorie des Nombres, Gauthier-Villars, Paris, 1891, Vol. 1. [Annotated scan of pages 488-499 only]
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MATHEMATICA
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h[1] = 2; h[n_] := h[n] = 2+Sum[(-1)^(i+1)*Product[h[n-i]-k, {k, 0, i}]/(i+1)!, {i, 1, n-1}]; a[0] = 1; a[n_] := h[n+1] - h[n]; Table[a[n], {n, 0, 10}] (* Jean-François Alcover, Dec 05 2013 *)
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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STATUS
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approved
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