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 A300477 Number of positive integers k with 1 < k < n such that n^k + k^n is prime. 2

%I

%S 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,

%T 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,

%U 0,0,0,0,0,1,1,0,0,0,0,1,0,0,0,0,0,1,0

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

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

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

%H Robert Israel, <a href="/A300477/b300477.txt">Table of n, a(n) for n = 2..1940</a>

%p f:= n -> nops(select(isprime, [seq(n^k-k^n,k=2..n-1)])):

%p map(f, [\$2..100]); # _Robert Israel_, Sep 24 2020

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

%Y Cf. A162488, A300478.

%K nonn

%O 2

%A _Felix FrÃ¶hlich_, Mar 06 2018

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Last modified May 29 08:14 EDT 2022. Contains 354124 sequences. (Running on oeis4.)