%I #23 Jun 07 2023 08:30:13

%S 5,67,70,22,1,43,25,40,4,53,23,49,8,7,26,52,77,16,13,2,14,41,17,68,71,

%T 76

%N Consider the English alphabet in Morse code (the International Morse radio telegraph code). Map a 'dit' to the digit one and a 'dah' to the digit 2, then express that ternary number in decimal.

%C Written in base 3, the terms read (12, 2111, 2121, 211, 1, 1121, 221, 1111, 11, 1222, 212, 1211, 22, 21, 222, 1221, 2212, 121, 111, 2, 112, 1112, 122, 2112, 2122, 2211). This contains all words over {1,2} with 1 to 4 letters except for 1122, 1212, 2221 and 2222, which correspond to the codes for Ü, Ä, Ö and CH. - _M. F. Hasler_, Jun 22 2020

%D "Learning the Radiotelegraph Code," Seventh Edition, published by American Radio Relay League, West Hartford 7, Connecticut, 1955.

%D "Morse Code Course," Jeppesen and Company, Denver, Colorado, 1962.

%D "International Morse Code," prepared by Lt. Commander F.R.L. Tuthill, USNR and Lt. (J.G.) E.L. Battey, USNR, published by Insuline Corporation of America, Long Island City, NY.

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Morse_code">Morse code</a>.

%e The sixth letter, F, is ".._." in Morse. This becomes 1121 in ternary and 43 in decimal, so a(6) = 43.

%o (PARI) A059852=digits(3008707498660932665486381130661318784490079420090,81) \\ or vecextract(apply(A032924,[1..28]), i) with i=numtoperm(26, 58849338891424664724588744) or i=vecsort(Vec("ETIANMSURWDKGOHVFuLaPJBXCYZQ"),,1)[1..26]. - _M. F. Hasler_, Jun 22 2020

%Y Cf. A060110, the same for numbers, and A060109, written in base 3.

%Y Cf. A008777 (number of base 3 digits = dots and dashes in the n-th letter), A281015, A281017, A281018.

%Y Cf. A105386, A105387 (ambiguous variants using digits 0 and 1).

%K base,easy,fini,full,nonn,word

%O 1,1

%A _Robert G. Wilson v_, Feb 27 2001

%E Edited, links and crossrefs added by _M. F. Hasler_, Jun 22 2020