A281015 Numbers with a prime number of dots in their International Morse numeral representation.

2, 3, 5, 7, 8, 11, 12, 14, 16, 18, 19, 20, 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, 80, 81, 83, 85, 87, 89, 91, 92, 94, 96, 98, 99, 101, 102, 104, 106, 108, 109, 110, 111, 113, 115, 117, 119, 120, 122, 124, 126

Offset

1,1

Comments

The Morse code is written in current ITU standard.

Indices of primes in A280913. - M. F. Hasler, Jun 22 2020

Links

Indranil Ghosh, Table of n, a(n) for n = 1..10000

Wikipedia, Morse Code

Example

27 is in the sequence because 27 in its Morse numeral representation is written as '..--- --...' which has 5 dots and 5 is prime.

Prog

(Python) # uses[A280913]
from sympy import isprime
i=0
j=1
while j<=100:
    if isprime(A280913(i)):
        print(str(j)+" "+str(i))
        j+=1
    i+=1
(PARI) select( {is_A281015(n)=isprime(A280913(n))}, [0..150]) \\ M. F. Hasler, Jun 22 2020

Crossrefs

Cf. A060109 (Morse code for n), A280913 (number of dots in Morse code for n).

Cf. A281017 (same for dashes), A281018 (intersection of the two).

Cf. A280998, A280999.

Sequence in context: A284655 A083028 A370867 * A288625 A189168 A182799

Adjacent sequences: A281012 A281013 A281014 * A281016 A281017 A281018

Keyword

nonn,base

Author

Indranil Ghosh, Jan 13 2017

Status

approved