

A281018


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


4



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
(list;
graph;
refs;
listen;
history;
text;
internal format)



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



