cp's OEIS Frontend

A242554 Least number k such that n^16 + k^16 is prime.

%I A242554 #12 Dec 26 2024 19:53:24
%S A242554 1,1,4,3,6,5,6,7,22,13,16,5,8,5,14,11,10,7,16,31,8,9,10,11,38,29,10,9,
%T A242554 22,61,20,5,4,3,16,11,6,25,28,7,6,17,16,1,46,9,58,61,22,41,92,3,14,19,
%U A242554 14,23,56,37,20,109,6,121,10,39,4,67,34,11,26,9,30,11,12,1
%N A242554 Least number k such that n^16 + k^16 is prime.
%C A242554 If a(n) = 1, then n is in A006313.
%e A242554 4^16+1^16 = 4294967297 is not prime. 4^16+2^16 = 4295032832 is not prime. 4^16+3^16 = 4338014017 is prime. Thus, a(4) = 3.
%o A242554 (Python)
%o A242554 import sympy
%o A242554 from sympy import isprime
%o A242554 def a(n):
%o A242554   for k in range(10**4):
%o A242554     if isprime(n**16+k**16):
%o A242554       return k
%o A242554 n = 1
%o A242554 while n < 100:
%o A242554   print(a(n))
%o A242554   n += 1
%o A242554 (PARI) a(n)=for(k=1,oo,if(ispseudoprime(n^16+k^16),return(k)));
%Y A242554 Cf. A069003, A006313.
%K A242554 nonn
%O A242554 1,3
%A A242554 _Derek Orr_, May 17 2014