A242557 Least number k such that n^128+k^128 is prime.

1, 113, 106, 259, 304, 85, 212, 135, 158, 47, 62, 985, 84, 47, 518, 485, 178, 169, 106, 27, 88, 139, 632, 47, 44, 643, 20, 209, 606, 1529, 32, 31, 1094, 139, 754, 647, 38, 37, 262, 69, 94, 631, 90, 25, 38, 195, 10, 277, 232, 187, 554, 189, 10, 47, 216, 131, 1132, 173, 390

Offset

1,2

Comments

If a(n) = 1, then n is in A056994.

Links

Table of n, a(n) for n=1..59.

Mathematica

lnk[n_]:=Module[{c=n^128, k}, k=If[EvenQ[c], 1, 2]; While[!PrimeQ[c+ k^128], k = k+2]; k]; Join[{1}, Array[lnk, 60, 2]] (* Harvey P. Dale, Mar 17 2015 *)

Prog

(Python)
import sympy
from sympy import isprime
def a(n):
    for k in range(10**4):
        if isprime(n**128+k**128):
            return k
n = 1
while n < 100:
    print(a(n))
    n += 1
(PARI) a(n)=for(k=1, 10^4, if(ispseudoprime(n^128+k^128), return(k)));
n=1; while(n<100, print(a(n)); n+=1)

Crossrefs

Cf. A069003, A056994.

Sequence in context: A115486 A157885 A204377 * A345072 A214503 A054033

Adjacent sequences: A242554 A242555 A242556 * A242558 A242559 A242560

Keyword

nonn

Author

Derek Orr, May 17 2014

Status

approved