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A242557 Least number k such that n^128+k^128 is prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 26 05:58 EDT 2021. Contains 348257 sequences. (Running on oeis4.)