A360508 - OEIS

A360508

Numbers k such that A300570(k) considered simply as a decimal string is prime.

2, 4, 13, 57, 64, 349

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

OFFSET

1,1

LINKS

EXAMPLE

A300570(4) = 10011101 = A000040(665267) is prime, so 4 is a term.

A300570(5) = 10110011101 = 6389*1582409 is composite, so 5 is not a term.

MATHEMATICA

Select[Range[350], PrimeQ[FromDigits[Flatten[IntegerDigits[Range[#, 1, -1], 2]]]] &] (* Amiram Eldar, Feb 19 2023 *)

PROG

(Python)

from sympy import isprime

from itertools import count, islice

def agen(): # generator of terms

s = ""

for k in count(1):

s = bin(k)[2:] + s

if isprime(int(s)): yield k

print(list(islice(agen(), 5))) # Michael S. Branicky, Feb 19 2023

CROSSREFS

Cf. A300570, A098780 (A300570 converted to base 10), A348792 (primes in A098780).

KEYWORD

nonn,base,more

AUTHOR

EXTENSIONS

a(6) from Alois P. Heinz, Feb 19 2023

STATUS

approved