A240503 Numbers k such that 5^k - 4^k - 3^k - 2^k - 1 is prime.

4, 8, 72, 396, 4428, 63152

Offset

1,1

Comments

a(7) > 70000. - Giovanni Resta, Apr 09 2014

a(7) > 110000. - Michael S. Branicky, Jul 06 2024

Links

Table of n, a(n) for n=1..6.

Example

5^4-4^4-3^4-2^4-1 = 271 is prime. Thus, 4 is a term of this sequence.

Prog

(PARI) for(n=1, 7500, if(ispseudoprime(5^n-4^n-3^n-2^n-1), print(n)))

Crossrefs

Cf. A000043, A240507.

Sequence in context: A013112 A274461 A206346 * A221484 A338314 A288956

Adjacent sequences: A240500 A240501 A240502 * A240504 A240505 A240506

Keyword

nonn,more

Author

Derek Orr, Apr 06 2014

Extensions

a(6) from Giovanni Resta, Apr 09 2014

Status

approved