cp's OEIS Frontend

A281017 Numbers with a prime number of dashes in their International Morse numeral representation.

%I A281017 #13 May 01 2021 08:03:56
%S A281017 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 A281017 47,49,50,52,53,57,58,61,63,64,66,67,69,70,72,74,75,76,78,81,83,85,87,
%U A281017 89,92,94,96,98,101,103,107,109,110,112,118,121,125,129,130,134,136,143
%N A281017 Numbers with a prime number of dashes in their International Morse numeral representation.
%C A281017 The Morse code is written in current ITU standard.
%C A281017 Indices of primes in A280916. - _M. F. Hasler_, Jun 22 2020
%H A281017 Indranil Ghosh, <a href="/A281017/b281017.txt">Table of n, a(n) for n = 1..10000</a>
%H A281017 Wikipedia, <a href="https://en.wikipedia.org/wiki/Morse_code">Morse Code</a>
%F A281017 This A281017 = { n | A280916(n) is prime }. - _M. F. Hasler_, Jun 22 2020
%e A281017 27 is in the sequence because 27 in its Morse numeral representation is written as '..--- --...' which has 5 dashes and 5 is prime.
%o A281017 (Python) # uses[A280916]
%o A281017 from sympy import isprime
%o A281017 i=0
%o A281017 j=1
%o A281017 while j<=100:
%o A281017     if isprime(A280916(i)):
%o A281017         print(str(j)+" "+str(i))
%o A281017         j+=1
%o A281017     i+=1
%o A281017 (PARI) select( {is_A281017(n)=isprime(A280916(n))}, [0..150]) \\ _M. F. Hasler_, Jun 22 2020
%Y A281017 Cf. A060109 (Morse code for n), A280916 (number of dashes in Morse code for n).
%Y A281017 Cf. A281015 (same for dots), A281018 (intersection of the two).
%Y A281017 Cf. A280998, A280999.
%K A281017 nonn,base
%O A281017 1,2
%A A281017 _Indranil Ghosh_, Jan 13 2017