A128027 -id:A128027 - cp's OEIS frontend

A230139 Numbers n such that (17^n - 4^n)/13 is prime.

3, 5, 7, 11, 31, 101, 887, 4861

Offset: 1

Robert Price, Oct 10 2013

All terms are prime.

a(9) > 10^5.

Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032, A210506, A128347, A128352, A225807.

Select[Prime[Range[1, 100000]], PrimeQ[(17^# - 4^#)/13]&]

is(n)=ispseudoprime((17^n-4^n)/13) \\ Charles R Greathouse IV, Jun 13 2017

A241921 Numbers k such that (15^k - 4^k)/11 is prime.

Original entry on oeis.org

2, 1097, 2243, 2857, 4357, 6803, 20747, 24571

Offset: 1

Robert Price, May 01 2014

All terms are prime.
a(9) > 10^5.
a(1) is trivially prime, the remainder are probable primes.

Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032, A210506, A128347, A225955, A062581.

Select[Prime[Range[1, 100000]], PrimeQ[(15^# - 4^#)/11]&]

is(n)=ispseudoprime((15^n-4^n)/11) \\ Charles R Greathouse IV, Jun 13 2017

A375620 Numbers k such that (20^k - 3^k)/17 is prime.

Original entry on oeis.org

2, 43, 1723, 2971, 3257, 12263, 38933

Offset: 1

William Dean, Aug 21 2024

All terms must be prime.

a(8) > 10^5.

			a(1) = 2 corresponds to the prime number 23.

OEIS Wiki, Primes of the form (a^n+b^n)/(a+b) and (a^n-b^n)/(a-b)

Cf. A028491, A057468, A128032, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032.

PARI
```
is(k) = ispseudoprime((20^k - 3^k)/17)
```

cp's OEIS Frontend

A230139 Numbers n such that (17^n - 4^n)/13 is prime.

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A241921 Numbers k such that (15^k - 4^k)/11 is prime.

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A375620 Numbers k such that (20^k - 3^k)/17 is prime.

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