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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.

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: A179535 A145414 A298106 * A166220 A121000 A290949

Adjacent sequences:  A266362 A266363 A266364 * A266366 A266367 A266368

KEYWORD

nonn

AUTHOR

Jonathan Sondow, Dec 28 2015

STATUS

approved

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Last modified April 9 17:48 EDT 2020. Contains 333361 sequences. (Running on oeis4.)