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%I #23 Dec 07 2018 18:26:42
%S 19,17,15,13,11,9,11,13,15,17,39,37,35,33,31,29,31,33,35,37,37,35,33,
%T 31,29,27,29,31,33,35,35,33,31,29,27,25,27,29,31,33,33,31,29,27,25,23,
%U 25,27,29,31,31,29,27,25,23,21,23,25,27,29,33,31,29,27,25,23,25,27,29,31,35,33,31,29,27,25,27
%N Duration of Morse code representation of n.
%C In the Morse Code (ITU) the time unit is the duration of a dot. A dash has duration of 3 dots. The space (s) between dots (d) and dashes (D) within a Morse code of a letter (here digit of a number) has duration of 1 dot. The separation (S) between two letter codes has duration of 3 dots. (The duration between two words (numbers) is 7 dots.)
%C Only odd numbers >= 9 appear.
%C There are duration twins for pairs (n-1, n) with n ending with digits 10, 20, 30, 40 or 50, except for n = 10. The digits 1 and 9, 2 and 8, and 3 and 7 are pairs with identical duration (of 17, 15, and 13, respectively).
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Morse_code">Morse code</a>
%F a(n) = S(n) + s(n) + dD(n), where S(n) = 3*(nrdigits(n) - 1), with nrdigits(n) the number of digits of n, s(n) = 4*nrdigits(n), and dD(n) = Sum_{j=1.. nrdigits(n)} 1*nrd(d_j) + 3*nrD(dj) = 1*A280913(n) + 3*A280916(n), with nrd(dj) the number of dots of the code of the j-th digits of n, and nrD(dj) the number of dashes of the code of the j-th digits of n.
%e n = 10: dsDsDsDsDSDsDsDsDsD, with a(10) = 3*(2-1) + 4*2 + ((1*1 + 3*4) + (1*0 + 3*5)) = 3 + 8 + (1*1 + 3*9) = 39.
%t nd[n_] := 15 - 2 * If[n<5, n, 10-n]; a[n_] := Module[{d = IntegerDigits[n]}, 7 * Length[d] - 3 + Total[nd/@ d]]; Array[a, 100, 0] (* _Amiram Eldar_, Dec 04 2018 *)
%Y Cf. A060109, A280913, A280916.
%K nonn,word,easy
%O 0,1
%A _Wolfdieter Lang_, Dec 03 2018
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