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

1,1

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