A281017 Numbers with a prime number of dashes in their International Morse numeral representation.

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

Offset: 1

Author

Indranil Ghosh, Jan 13 2017

Keywords

• nonn
• base

Comments

The Morse code is written in current ITU standard.

Indices of primes in A280916. - M. F. Hasler, Jun 22 2020

Examples

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

Links

• Indranil Ghosh, Table of n, a(n) for n = 1..10000
• Wikipedia, Morse Code

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.

Programs

PARI

select( {is_A281017(n)=isprime(A280916(n))}, [0..150]) \\ M. F. Hasler, Jun 22 2020

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

Formula

This A281017 = { n | A280916(n) is prime }. - M. F. Hasler, Jun 22 2020