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A224471 Numbers n such that 8^n - n is prime. 3
1, 3, 37, 45, 597, 1131, 14203, 112539 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(8) > 41000. - Giovanni Resta, Apr 07 2013

a(9) > 2*10^5. - Robert Price, Jan 19 2014

LINKS

Table of n, a(n) for n=1..8.

MAPLE

A224471:=proc(q) local n;

for n from 1 to q do if isprime(8^n-n) then print(n); fi; od; end:

A224471(15000); # Paolo P. Lava, Apr 19 2013

PROG

(Java)

import java.math.BigInteger;

public class A224471 {

  public static void main (String[] args) {

    BigInteger b8 = BigInteger.valueOf(8);

    BigInteger m = BigInteger.valueOf(64);

    for(long n=1; ; n+=2) {

        BigInteger b = b8.subtract(BigInteger.valueOf(n));

        if (b.isProbablePrime(2)) {

            if (b.isProbablePrime(80))

                System.out.printf("%d\n", n);

        }

        b8 = b8.multiply(m);

    }

  }

}

(PARI) forstep(n=1, 10^4, 2, if(ispseudoprime(8^n-n), print1(n, ", "))); /* Joerg Arndt, Apr 07 2013 */

CROSSREFS

Cf. A048744, A058037, A057908, A058046, A058829, A224470, A224469, A224469.

Sequence in context: A037000 A042333 A106103 * A286637 A106996 A338751

Adjacent sequences:  A224468 A224469 A224470 * A224472 A224473 A224474

KEYWORD

nonn,hard,more

AUTHOR

Alex Ratushnyak, Apr 06 2013

EXTENSIONS

a(7) from Giovanni Resta, Apr 07 2013

a(8) from Robert Price, Jan 19 2014

STATUS

approved

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Last modified July 30 21:33 EDT 2021. Contains 346365 sequences. (Running on oeis4.)