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 A266365 Number of possible plugboard settings for a WWII German Enigma Cipher Machine with n cables. 1
 1, 325, 44850, 3453450, 164038875, 5019589575, 100391791500, 1305093289500, 10767019638375, 53835098191875, 150738274937250, 205552193096250, 102776096548125, 7905853580625, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) increases to a maximum at n = 11, then decreases. REFERENCES Andrew Hodges, Alan Turing: the Enigma, Princeton University Press, 2014. LINKS Table of n, a(n) for n=0..16. A. Ray Miller, The Cryptographic Mathematics of Enigma, Cryptologia, 19 (1995), 65-80. Kalika Prasad and Munesh Kumari, A review on mathematical strength and analysis of Enigma, arXiv:2004.09982 [cs.CR], 2020. Tony Sale, Counting the Possible Plugboard Setting, Codes and Ciphers, Enigma. FORMULA a(n) = 26! / ((26 - 2n)! n! 2^n) = C(2,26,n) (see A181386). MATHEMATICA Table[26!/((26 - 2 n)! n! 2^n), {n, 0, 16}] CROSSREFS Cf. A181386. Sequence in context: A374257 A145414 A298106 * A340462 A166220 A121000 Adjacent sequences: A266362 A266363 A266364 * A266366 A266367 A266368 KEYWORD nonn AUTHOR Jonathan Sondow, Dec 28 2015 STATUS approved

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Last modified August 6 14:16 EDT 2024. Contains 374974 sequences. (Running on oeis4.)