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A007346
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Order of group generated by perfect shuffles of 2n cards.
(Formerly M1909)
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1
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2, 8, 24, 24, 1920, 7680, 322560, 64, 92897280, 3715891200, 40874803200, 194641920, 25505877196800, 1428329123020800, 21424936845312000, 160, 23310331287699456000, 1678343852714360832000, 31888533201572855808000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| P. Diaconis, R. L. Graham and W. M. Kantor, The mathematics of perfect shuffles, Adv. Appl. Math., 4 (1983), 175-196.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Index entries for sequences related to groups
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PROG
| (PARI) A007346(n) = local(M); M=2^n*n!; if(n%4==2, if(n==2, 8, if(n==6, M/6, M)), if(n%4==1, if(n==1, 2, M/2), if(n%4==3, M/2, if(n==2^valuation(n, 2), 2*n*(valuation(n, 2)+1), if(n==12, M/(7!*2), M/4))))) - Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Nov 30 2006
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CROSSREFS
| Sequence in context: A018042 A072842 A138387 * A062247 A171261 A084744
Adjacent sequences: A007343 A007344 A007345 * A007347 A007348 A007349
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KEYWORD
| nonn,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein (mira(AT)math.berkeley.edu)
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EXTENSIONS
| Corrected and extended by Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Nov 30 2006
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