A242554 - OEIS

%I #5 May 17 2014 12:44:11

%S 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 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 14,23,56,37,20,109,6,121,10,39,4,67,34,11,26,9,30,11,12,1

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

%C If a(n) = 1, then n is in A006313.

%e 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 (Python)

%o import sympy

%o from sympy import isprime

%o def a(n):

%o ..for k in range(10**4):

%o ....if isprime(n**16+k**16):

%o ......return k

%o n = 1

%o while n < 100:

%o ..print(a(n))

%o ..n += 1

%o (PARI) a(n)=for(k=1,10^3,if(ispseudoprime(n^16+k^16),return(k)));

%o n=1;while(n<100,print(a(n));n+=1)

%Y Cf. A069003, A006313.

%K nonn

%O 1,3

%A _Derek Orr_, May 17 2014