A241427 Smallest prime of the form n^k - k^n for some k, or 0 if no such prime exists.

7, 2, 3, 6102977801, 5, 79792265017612001, 7, 2486784401

Offset

2,1

Comments

Conjecture: a(n) > 0 for all n not in A097764.

More terms in b-file. If n > 4 and in A097764, n^k - k^n is factorable and won't be prime.

a(17) > 17^7500 - 7500^17. See A239279.

Links

Derek Orr, Table of n, a(n) for n = 2..16

Prog

(PARI)
a(n)=k=1; if(n>4, forprime(p=1, 100, if(ispower(n)&&ispower(n)%p==0&&n%p==0, return(0)); if(n%p==n, break))); k=1; while(!ispseudoprime(n^k-k^n), k++); return(n^k-k^n)
vector(15, n, a(n+1))

Crossrefs

Cf. A078201.

Sequence in context: A248288 A248287 A233929 * A197761 A199269 A021584

Adjacent sequences: A241424 A241425 A241426 * A241428 A241429 A241430

Keyword

nonn

Author

Derek Orr, Aug 08 2014

Status

approved