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%I #13 May 01 2021 08:03:56
%S 0,2,3,7,8,12,14,16,18,21,23,25,27,29,30,32,34,35,36,38,41,43,44,46,
%T 47,49,50,52,53,57,58,61,63,64,66,67,69,70,72,74,75,76,78,81,83,85,87,
%U 89,92,94,96,98,101,103,107,109,110,112,118,121,125,129,130,134,136,143
%N Numbers with a prime number of dashes in their International Morse numeral representation.
%C The Morse code is written in current ITU standard.
%C Indices of primes in A280916. - _M. F. Hasler_, Jun 22 2020
%H Indranil Ghosh, <a href="/A281017/b281017.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>
%F This A281017 = { n | A280916(n) is prime }. - _M. F. Hasler_, Jun 22 2020
%e 27 is in the sequence because 27 in its Morse numeral representation is written as '..--- --...' which has 5 dashes and 5 is prime.
%o (Python) # uses[A280916]
%o from sympy import isprime
%o i=0
%o j=1
%o while j<=100:
%o if isprime(A280916(i)):
%o print(str(j)+" "+str(i))
%o j+=1
%o i+=1
%o (PARI) select( {is_A281017(n)=isprime(A280916(n))}, [0..150]) \\ _M. F. Hasler_, Jun 22 2020
%Y Cf. A060109 (Morse code for n), A280916 (number of dashes in Morse code for n).
%Y Cf. A281015 (same for dots), A281018 (intersection of the two).
%Y Cf. A280998, A280999.
%K nonn,base
%O 1,2
%A _Indranil Ghosh_, Jan 13 2017
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