A300477 Number of positive integers k with 1 < k < n such that n^k + k^n is prime.

0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0

Offset

2

Comments

a(n) > 0 iff n is a term of A162488.

a(n) > 1 iff n is a term of A300478.

Links

Robert Israel, Table of n, a(n) for n = 2..1940

Maple

f:= n -> nops(select(isprime, [seq(n^k-k^n, k=2..n-1)])):
map(f, [$2..100]); # Robert Israel, Sep 24 2020

Prog

(PARI) a(n) = my(i=0); for(k=2, n-1, if(ispseudoprime(n^k+k^n), i++)); i

Crossrefs

Cf. A162488, A300478.

Sequence in context: A025464 A162518 A330306 * A355202 A353556 A228495

Adjacent sequences: A300474 A300475 A300476 * A300478 A300479 A300480

Keyword

nonn

Author

Felix Fröhlich, Mar 06 2018

Status

approved