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 A281017 Numbers with a prime number of dashes in their International Morse numeral representation. 5
 0, 2, 3, 7, 8, 12, 14, 16, 18, 21, 23, 25, 27, 29, 30, 32, 34, 35, 36, 38, 41, 43, 44, 46, 47, 49, 50, 52, 53, 57, 58, 61, 63, 64, 66, 67, 69, 70, 72, 74, 75, 76, 78, 81, 83, 85, 87, 89, 92, 94, 96, 98, 101, 103, 107, 109, 110, 112, 118, 121, 125, 129, 130, 134, 136, 143 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The Morse code is written in current ITU standard. Indices of primes in A280916. - M. F. Hasler, Jun 22 2020 LINKS Indranil Ghosh, Table of n, a(n) for n = 1..10000 Wikipedia, Morse Code FORMULA This A281017 = { n | A280916(n) is prime }. - M. F. Hasler, Jun 22 2020 EXAMPLE 27 is in the sequence because 27 in its Morse numeral representation is written as '..--- --...' which has 5 dashes and 5 is prime. PROG (Python) # uses[A280916] from sympy import isprime i=0 j=1 while j<=100:     if isprime(A280916(i)):         print(str(j)+" "+str(i))         j+=1     i+=1 (PARI) select( {is_A281017(n)=isprime(A280916(n))}, [0..150]) \\ M. F. Hasler, Jun 22 2020 CROSSREFS Cf. A060109 (Morse code for n), A280916 (number of dashes in Morse code for n). Cf. A281015 (same for dots), A281018 (intersection of the two). Cf. A280998, A280999. Sequence in context: A331078 A032967 A111101 * A281018 A184860 A242655 Adjacent sequences:  A281014 A281015 A281016 * A281018 A281019 A281020 KEYWORD nonn,base AUTHOR Indranil Ghosh, Jan 13 2017 STATUS approved

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Last modified August 4 18:15 EDT 2021. Contains 346455 sequences. (Running on oeis4.)