A058994 Numbers m such that 7^m reversed is prime.

1, 12, 24, 225, 392, 819, 1201, 1645, 1775, 37578

Offset: 1

Author

Robert G. Wilson v, Jan 17 2001

Keywords

• nonn
• base
• more

Crossrefs

Cf. A059208, A071584.

Numbers m such that k^m reversed is prime: A057708 (k=2), A350441 (k=4), A058993 (k=5), this sequence (k=7), A350442 (k=8), A058995 (k=13).

Programs

Mathematica

Do[ If[ PrimeQ[ ToExpression[ StringReverse[ ToString[7^n] ] ] ], Print[n] ], {n, 1, 2500} ]

PARI

isok(m) = isprime(fromdigits(Vecrev(digits(7^m)))) \\ Mohammed Yaseen, Jul 20 2022

Python

from sympy import isprime
k, m, A058994_list = 1, 7,  []
while k <= 10**3:
    if isprime(int(str(m)[::-1])):
        A058994_list.append(k)
    k += 1
    m *= 7 # Chai Wah Wu, Mar 09 2021

Extensions

a(10) from Michael S. Branicky, Mar 16 2025