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A266365
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Number of possible plugboard settings for a WWII German Enigma Cipher Machine with n cables.
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1
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1, 325, 44850, 3453450, 164038875, 5019589575, 100391791500, 1305093289500, 10767019638375, 53835098191875, 150738274937250, 205552193096250, 102776096548125, 7905853580625, 0, 0, 0
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OFFSET
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0,2
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COMMENTS
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a(n) increases to a maximum at n = 11, then decreases.
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REFERENCES
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Andrew Hodges, Alan Turing: the Enigma, Princeton University Press, 2014.
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LINKS
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FORMULA
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a(n) = 26! / ((26 - 2n)! n! 2^n) = C(2,26,n) (see A181386).
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MATHEMATICA
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Table[26!/((26 - 2 n)! n! 2^n), {n, 0, 16}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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