A281018 -id:A281018 - cp's OEIS frontend

A059852 Consider the English alphabet in Morse code (the International Morse radio telegraph code). Map a 'dit' to the digit one and a 'dah' to the digit 2, then express that ternary number in decimal.

5, 67, 70, 22, 1, 43, 25, 40, 4, 53, 23, 49, 8, 7, 26, 52, 77, 16, 13, 2, 14, 41, 17, 68, 71, 76

Offset: 1

Robert G. Wilson v, Feb 27 2001

Written in base 3, the terms read (12, 2111, 2121, 211, 1, 1121, 221, 1111, 11, 1222, 212, 1211, 22, 21, 222, 1221, 2212, 121, 111, 2, 112, 1112, 122, 2112, 2122, 2211). This contains all words over {1,2} with 1 to 4 letters except for 1122, 1212, 2221 and 2222, which correspond to the codes for Ü, Ä, Ö and CH. - M. F. Hasler, Jun 22 2020

			The sixth letter, F, is ".._." in Morse. This becomes 1121 in ternary and 43 in decimal, so a(6) = 43.

"Learning the Radiotelegraph Code," Seventh Edition, published by American Radio Relay League, West Hartford 7, Connecticut, 1955.
"Morse Code Course," Jeppesen and Company, Denver, Colorado, 1962.
"International Morse Code," prepared by Lt. Commander F.R.L. Tuthill, USNR and Lt. (J.G.) E.L. Battey, USNR, published by Insuline Corporation of America, Long Island City, NY.

Wikipedia, Morse code.

Cf. A060110, the same for numbers, and A060109, written in base 3.
Cf. A008777 (number of base 3 digits = dots and dashes in the n-th letter), A281015, A281017, A281018.
Cf. A105386, A105387 (ambiguous variants using digits 0 and 1).

A059852=digits(3008707498660932665486381130661318784490079420090,81) \\ or vecextract(apply(A032924,[1..28]), i) with i=numtoperm(26, 58849338891424664724588744) or i=vecsort(Vec("ETIANMSURWDKGOHVFuLaPJBXCYZQ"),,1)[1..26]. - M. F. Hasler, Jun 22 2020

Edited, links and crossrefs added by M. F. Hasler, Jun 22 2020

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

Original entry on oeis.org

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

Indranil Ghosh, Jan 13 2017

The Morse code is written in current ITU standard.

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

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

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

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.

select( {is_A281015(n)=isprime(A280913(n))}, [0..150]) \\ M. F. Hasler, Jun 22 2020

# 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

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

Original entry on oeis.org

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

Indranil Ghosh, Jan 13 2017

The Morse code is written in current ITU standard.

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

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

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

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.

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

# 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

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

cp's OEIS Frontend

A059852 Consider the English alphabet in Morse code (the International Morse radio telegraph code). Map a 'dit' to the digit one and a 'dah' to the digit 2, then express that ternary number in decimal.

Views

Author

Keywords

Comments

Examples

References

Links

Crossrefs

Programs

PARI

Extensions

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

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

PARI

Python

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

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

PARI

Python

Formula