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Search: id:A001472
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| A001472 |
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Number of degree-n permutations of order dividing 4.
(Formerly M1292 N0495)
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+0
38
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| 1, 1, 2, 4, 16, 56, 256, 1072, 6224, 33616, 218656, 1326656, 9893632, 70186624, 574017536, 4454046976, 40073925376, 347165733632, 3370414011904, 31426411211776, 328454079574016, 3331595921852416, 37125035407900672, 400800185285464064
(list; graph; listen)
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OFFSET
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0,3
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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).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
L. Moser and M. Wyman, On solutions of x^d = 1 in symmetric groups, Canad. J. Math., 7 (1955), 159-168.
R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Example 5.2.10.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..200
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 25
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FORMULA
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E.g.f.: exp(x+1/2*x^2+1/4*x^4).
a(0)=1, a(1)=1, a(2)=2, a(3)=4, a(n)=a(n-1)+(n-1)*a(n-2)+(n^3-6n^2+11n-6)*a(n-4) for n>3. [From H. Palsdottir (hronn07(AT)ru.is), Sep 19 2008]
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CROSSREFS
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Cf. A000085, A001470, A053495.
Sequence in context: A104354 A153948 A010362 this_sequence A053498 A005388 A053503
Adjacent sequences: A001469 A001470 A001471 this_sequence A001473 A001474 A001475
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com) and J. H. Conway (conway(AT)math.princeton.edu)
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