A108879 -id:A108879 - cp's OEIS frontend

A108318 Numbers k such that (k+1)*k^k - 1 is prime.

2, 3, 4, 5, 7, 11, 15, 26, 52, 116, 359, 1547, 2465

Offset: 1

Ray G. Opao, Jun 30 2005

a(14) > 15000. - Michael S. Branicky, Oct 01 2024

			15 is in the sequence because (15+1)*15^15-1 = 16*15^15-1 = 7006302246093749999, which is prime.

Cf. A108879.

[n: n in [1..1000] |IsPrime((n+1)*n^n-1)]; // Vincenzo Librandi, Oct 23 2014

Select[Range[1000], PrimeQ[(# + 1) #^# - 1] &] (* Vincenzo Librandi, Oct 23 2014 *)

isok(n) = isprime((n+1)*n^n-1); \\ Michel Marcus, Oct 23 2014

A353122 Numbers k such that k^k*(k+1) + 1 is prime.

Original entry on oeis.org

0, 1, 2, 3, 6, 9, 186, 198, 8390

Offset: 1

Juri-Stepan Gerasimov, Apr 24 2022

Corresponding primes start 2, 3, 13, 109, 326593, 3874204891, ...
a(9) > 6000. - Jon E. Schoenfield, Jun 05 2022
a(10) > 18000. - Michael S. Branicky, Aug 08 2024

			9 is in the sequence because 9^9*(9+1) + 1 = 3874204891, which is prime.

Cf. A055897, A081132, A108318, A108879, A191513, A191568, A271718.

[n: n in [0..200] | IsPrime(n^n*(n+1) + 1)];

Join[{0}, Select[Range[200], PrimeQ[#^#*(# + 1) + 1] &]] (* Amiram Eldar, Apr 25 2022 *)

isok(k) = ispseudoprime(k^k*(k+1) + 1); \\ Michel Marcus, May 16 2022

a(9) from Michael S. Branicky, Dec 22 2023

cp's OEIS Frontend

A108318 Numbers k such that (k+1)*k^k - 1 is prime.

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