cp's OEIS Frontend

A281018 Numbers with a prime number of dots and a prime number of dashes in their International Morse numeral representation.

%I A281018 #18 May 03 2021 15:37:11
%S A281018 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 A281018 58,61,63,67,69,70,72,74,76,78,81,83,85,87,89,92,94,96,98,101,109,110,
%U A281018 190,200,355,445,454,456,465,535,544,546,553,557,564,566,575,645
%N A281018 Numbers with a prime number of dots and a prime number of dashes in their International Morse numeral representation.
%C A281018 This uses the current ITU standard Morse code.
%C A281018 This sequence is the intersection of A281015 and A281017.
%H A281018 Indranil Ghosh, <a href="/A281018/b281018.txt">Table of n, a(n) for n = 1..10000</a>
%H A281018 Wikipedia, <a href="https://en.wikipedia.org/wiki/Morse_code">Morse Code</a>
%e A281018 27 is in the sequence because it is both in A281015 and A281017.
%o A281018 (Python) # uses[A280913, A280916]
%o A281018 from sympy import isprime
%o A281018 i=0
%o A281018 j=1
%o A281018 while j<=1000:
%o A281018     if isprime(A280913(i)) and isprime(A280916(i)):
%o A281018         print(str(j)+" "+str(i))
%o A281018         j+=1
%o A281018     i+=1
%o A281018 (PARI) select( {is_A281018(n)=is_A281017(n)&&is_A281015(n)}, [0..666]) \\ _M. F. Hasler_, Jun 22 2020
%Y A281018 Cf. A280913, A280916, A281015, A281017.
%Y A281018 Cf. A060109 (Morse code for n).
%K A281018 nonn,base
%O A281018 1,1
%A A281018 _Indranil Ghosh_, Jan 13 2017