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%I #15 May 01 2021 08:02:49
%S 2,3,5,7,8,11,12,14,16,18,19,20,21,23,25,27,29,30,32,34,36,38,41,43,
%T 47,49,50,52,58,61,63,67,69,70,72,74,76,78,80,81,83,85,87,89,91,92,94,
%U 96,98,99,101,102,104,106,108,109,110,111,113,115,117,119,120,122,124,126
%N Numbers with a prime number of dots in their International Morse numeral representation.
%C The Morse code is written in current ITU standard.
%C Indices of primes in A280913. - _M. F. Hasler_, Jun 22 2020
%H Indranil Ghosh, <a href="/A281015/b281015.txt">Table of n, a(n) for n = 1..10000</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Morse_code">Morse Code</a>
%e 27 is in the sequence because 27 in its Morse numeral representation is written as '..--- --...' which has 5 dots and 5 is prime.
%o (Python) # uses[A280913]
%o from sympy import isprime
%o i=0
%o j=1
%o while j<=100:
%o if isprime(A280913(i)):
%o print(str(j)+" "+str(i))
%o j+=1
%o i+=1
%o (PARI) select( {is_A281015(n)=isprime(A280913(n))}, [0..150]) \\ _M. F. Hasler_, Jun 22 2020
%Y Cf. A060109 (Morse code for n), A280913 (number of dots in Morse code for n).
%Y Cf. A281017 (same for dashes), A281018 (intersection of the two).
%Y Cf. A280998, A280999.
%K nonn,base
%O 1,1
%A _Indranil Ghosh_, Jan 13 2017
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