A058993 Numbers m such that 5^m reversed is a prime.

1, 3, 26, 36, 43, 66, 76, 149, 511, 885, 3767, 18157, 20516, 26316

Offset: 1

Author

Robert G. Wilson v, Jan 17 2001

Keywords

• nonn
• base
• more

Crossrefs

Cf. A059206, A071583.

Numbers m such that k^m reversed is prime: A057708 (k=2), A350441 (k=4), this sequence (k=5), A058994 (k=7), A350442 (k=8), A058995 (k=13).

Programs

Mathematica

Do[ If[ PrimeQ[ ToExpression[ StringReverse[ ToString[5^n] ] ] ], Print[n] ], {n, 1, 3000} ]

PARI

isok(m) = isprime(fromdigits(Vecrev(digits(5^m)))) \\ Mohammed Yaseen, Jul 20 2022

Python

from sympy import isprime
k, m, A058993_list = 1, 5,  []
while k <= 10**3:
    if isprime(int(str(m)[::-1])):
        A058993_list.append(k)
    k += 1
    m *= 5 # Chai Wah Wu, Mar 09 2021

Extensions

a(12)-a(14) from Michael S. Branicky, Apr 01 2023