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Numbers with a prime number of dots and a prime number of dashes in their International Morse numeral representation.
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%I #18 May 03 2021 15:37:11

%S 2,3,7,8,12,14,16,18,21,23,25,27,29,30,32,34,36,38,41,43,47,49,50,52,

%T 58,61,63,67,69,70,72,74,76,78,81,83,85,87,89,92,94,96,98,101,109,110,

%U 190,200,355,445,454,456,465,535,544,546,553,557,564,566,575,645

%N Numbers with a prime number of dots and a prime number of dashes in their International Morse numeral representation.

%C This uses the current ITU standard Morse code.

%C This sequence is the intersection of A281015 and A281017.

%H Indranil Ghosh, <a href="/A281018/b281018.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 it is both in A281015 and A281017.

%o (Python) # uses[A280913, A280916]

%o from sympy import isprime

%o i=0

%o j=1

%o while j<=1000:

%o if isprime(A280913(i)) and isprime(A280916(i)):

%o print(str(j)+" "+str(i))

%o j+=1

%o i+=1

%o (PARI) select( {is_A281018(n)=is_A281017(n)&&is_A281015(n)}, [0..666]) \\ _M. F. Hasler_, Jun 22 2020

%Y Cf. A280913, A280916, A281015, A281017.

%Y Cf. A060109 (Morse code for n).

%K nonn,base

%O 1,1

%A _Indranil Ghosh_, Jan 13 2017