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 A281018 Numbers with a prime number of dots and a prime number of dashes in their International Morse numeral representation. 4
 2, 3, 7, 8, 12, 14, 16, 18, 21, 23, 25, 27, 29, 30, 32, 34, 36, 38, 41, 43, 47, 49, 50, 52, 58, 61, 63, 67, 69, 70, 72, 74, 76, 78, 81, 83, 85, 87, 89, 92, 94, 96, 98, 101, 109, 110, 190, 200, 355, 445, 454, 456, 465, 535, 544, 546, 553, 557, 564, 566, 575, 645 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This uses the current ITU standard Morse code. This sequence is the intersection of A281015 and A281017. LINKS Indranil Ghosh, Table of n, a(n) for n = 1..10000 Wikipedia, Morse Code EXAMPLE 27 is in the sequence because it is both in A281015 and A281017. PROG (Python) # uses[A280913, A280916] from sympy import isprime i=0 j=1 while j<=1000:     if isprime(A280913(i)) and isprime(A280916(i)):         print(str(j)+" "+str(i))         j+=1     i+=1 (PARI) select( {is_A281018(n)=is_A281017(n)&&is_A281015(n)}, [0..666]) \\ M. F. Hasler, Jun 22 2020 CROSSREFS Cf. A280913, A280916, A281015, A281017. Cf. A060109 (Morse code for n). Sequence in context: A032967 A111101 A281017 * A184860 A242655 A145489 Adjacent sequences:  A281015 A281016 A281017 * A281019 A281020 A281021 KEYWORD nonn,base AUTHOR Indranil Ghosh, Jan 13 2017 STATUS approved

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Last modified August 3 07:47 EDT 2021. Contains 346435 sequences. (Running on oeis4.)