A054462 Numbers k such that (k+1)^k + k^(k-1) is prime.

1, 2, 3, 8, 9, 15, 16, 219

Offset

1,2

Comments

a(9) > 5000, if it exists. - Amiram Eldar, Jun 28 2024

a(9) > 25000, if it exists. - Michael S. Branicky, Jan 08 2025

Links

Table of n, a(n) for n=1..8.

Mathematica

Select[Range[1000], PrimeQ[(# + 1)^# + #^(# - 1)] &] (* Vincenzo Librandi, Sep 27 2012 *)

Prog

(PARI) xp1toxp1(n)= { my(y); forstep(x=1, n, 1, y=(x+1)^x + x^(x-1); if(ispseudoprime(y), print1(x, ", ")) ); }

Crossrefs

Cf. A389195.

Sequence in context: A029787 A382763 A246396 * A101471 A137471 A051209

Adjacent sequences: A054459 A054460 A054461 * A054463 A054464 A054465

Keyword

nonn,hard,more

Author

Cino Hilliard, Aug 30 2003

Extensions

a(1)=1 inserted by Vincenzo Librandi, Sep 27 2012

Status

approved