

A242553


Least number k such that n^8+k^8 is prime.


1



1, 1, 10, 1, 6, 5, 12, 13, 16, 3, 24, 7, 2, 3, 8, 9, 4, 17, 4, 7, 2, 3, 20, 7, 8, 19, 10, 3, 10, 19, 14, 17, 32, 11, 8, 25, 6, 25, 40, 7, 10, 43, 16, 5, 68, 7, 30, 5, 8, 19, 58, 17, 26, 17, 2, 11, 10, 3, 4, 49, 6, 71, 22, 15, 14, 47, 30, 9, 2, 19, 6, 19, 6, 5, 28, 13, 2
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OFFSET

1,3


COMMENTS



LINKS



EXAMPLE

10^8+1^8 = 100000001 is not prime. 10^8+2^8 = 100000256 is not prime. 10^8+3^8 = 100006561 is prime. Thus, a(10) = 3.


MATHEMATICA

lnk[n_]:=Module[{c=n^8, k=1}, While[CompositeQ[c+k^8], k++]; k]; Array[lnk, 80] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 12 2020 *)


PROG

(Python)
import sympy
from sympy import isprime
def a(n):
..for k in range(10**4):
....if isprime(n**8+k**8):
......return k
n = 1
while n < 100:
..print(a(n))
..n += 1
(PARI) a(n)=for(k=1, 10^3, if(ispseudoprime(n^8+k^8), return(k)));
n=1; while(n<100, print(a(n)); n+=1)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



