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

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

Offset: 1

Author

Indranil Ghosh, Jan 13 2017

Keywords

• nonn
• base

Comments

This uses the current ITU standard Morse code.

This sequence is the intersection of A281015 and A281017.

Examples

			27 is in the sequence because it is both in A281015 and A281017.
		

Links

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

Crossrefs

Cf. A280913, A280916, A281015, A281017.

Cf. A060109 (Morse code for n).

Programs

PARI

select( {is_A281018(n)=is_A281017(n)&&is_A281015(n)}, [0..666]) \\ M. F. Hasler, Jun 22 2020

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