A217353 -id:A217353 - cp's OEIS frontend

A217354 Numbers n such that 8^n + 3 is prime.

1, 2, 4, 5, 6, 10, 28, 76, 130, 370, 568, 713, 789, 790, 1334, 1354, 1849, 2913, 5729, 5740, 5978, 6908, 10618, 11918, 12748, 13449, 40850, 68654, 78442, 121040, 159948, 228526

Offset: 1

Vincenzo Librandi, Oct 02 2012

nonn

3*A217354 is a subsequence of A057732. - Bruno Berselli, Oct 02 2012

Cf. A057732, A089437, A217353.

Mathematica
```
Select[Range[5000], PrimeQ[8^# + 3] &]
```

is(n)=ispseudoprime(8^n+3) \\ Charles R Greathouse IV, Feb 17 2017

a(19)-a(32) are obtained from A057732; by Bruno Berselli, Oct 02 2012

A217380 Numbers k such that 8^k - 7 is prime.

Original entry on oeis.org

13, 661, 773, 833, 4273, 40613, 302913

Offset: 1

Vincenzo Librandi, Oct 02 2012

All terms are equal to 1/3 of the multiples of 3 in A059609.

Naturally these numbers are odd since (9-1)^(2n)-7 is divisible by 3. - Bruno Berselli, Oct 04 2012

Cf. A059609, A217353, A217356.

Mathematica
```
Select[Range[4000], PrimeQ[8^# - 7] &]
```

is(n)=ispseudoprime(8^n-7) \\ Charles R Greathouse IV, Jun 13 2017

a(7) using A059609 from Michael S. Branicky, Sep 15 2024

cp's OEIS Frontend

A217354 Numbers n such that 8^n + 3 is prime.

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