A350441 Numbers m such that 4^m reversed is prime.

2, 5, 12, 35, 75, 182, 828, 1002, 1063, 2168, 6345, 6920, 10054, 14444, 51465

Offset

1,1

Comments

From Bernard Schott, Jan 30 2022: (Start)

If m is a term, then u = 2*m is a term of A057708, because 4^m = 2^(2*m). In fact, terms of this sequence here are half the even terms of A057708.

If m is a term that is multiple of 3, then k = 2*m/3 is a term of A350442, because 4^m = 8^(2m/3). First examples: m = 12, 75, 828, 1002, 6345, 51465, ... and corresponding k = 8, 50, 552, 668, 4230, 34310, ... (End)

Links

Table of n, a(n) for n=1..15.

Mathematica

Select[Range[2200], PrimeQ[IntegerReverse[4^#]] &] (* Amiram Eldar, Dec 31 2021 *)

Prog

(PARI) isok(m) = isprime(fromdigits(Vecrev(digits(4^m))))
(Python)
from sympy import isprime
m = 4
for n in range (1, 2000):
    if isprime(int(str(m)[::-1])):
        print(n)
    m *= 4

Crossrefs

Cf. A058996, A071582.

Cf. Numbers m such that k^m reversed is prime: A057708 (k=2), this sequence (k=4), A058993 (k=5), A058994 (k=7), A350442 (k=8), A058995 (k=13).

Sequence in context: A131467 A000103 A101292 * A181899 A131267 A266931

Adjacent sequences: A350438 A350439 A350440 * A350442 A350443 A350444

Keyword

nonn,base,more

Author

Mohammed Yaseen, Dec 31 2021

Extensions

a(11)-a(15) from Amiram Eldar, Dec 31 2021

Status

approved