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A242552 Least number k such that n^4+k^4 is prime. 0
1, 1, 2, 1, 2, 1, 2, 3, 2, 7, 2, 13, 4, 5, 8, 1, 2, 5, 2, 1, 10, 15, 2, 1, 6, 3, 2, 1, 12, 7, 12, 5, 14, 1, 6, 7, 2, 3, 14, 9, 2, 5, 10, 21, 2, 1, 4, 1, 2, 7, 2, 11, 6, 1, 14, 1, 2, 7, 2, 11, 2, 11, 8, 23, 16, 29, 12, 3, 10, 27, 2, 5, 8, 1, 8, 3, 20, 17, 2, 1, 10, 1, 10 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

If a(n) = 1, then n is in A000068.

LINKS

Table of n, a(n) for n=1..83.

EXAMPLE

8^4+1^4 = 4097 is not prime. 8^4+2^4 = 4112 is not prime. 8^4+3^4 = 4177 is prime. Thus, a(8) = 3.

PROG

(Python)

import sympy

from sympy import isprime

def a(n):

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

....if isprime(n**4+k**4):

......return k

n = 1

while n < 100:

..print(a(n))

..n += 1

(PARI) a(n)=for(k=1, 10^3, if(ispseudoprime(n^4+k^4), return(k)));

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

CROSSREFS

Cf. A069003, A000068.

Sequence in context: A060145 A257806 A035391 * A249717 A249718 A244518

Adjacent sequences:  A242549 A242550 A242551 * A242553 A242554 A242555

KEYWORD

nonn

AUTHOR

Derek Orr, May 17 2014

STATUS

approved

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Last modified January 29 01:54 EST 2020. Contains 331328 sequences. (Running on oeis4.)