A133834 Numbers k such that primorial(k)^4 + 1 is prime.

0, 1, 2, 4, 23, 76, 339, 1282

Offset: 1

Author

Rick L. Shepherd, Sep 26 2007

Keywords

• nonn
• hard
• more

Comments

Seven terms found and primes proved by PrimeForm ([N-1, Brillhart-Lehmer-Selfridge]). p(1282)#^4 + 1 has 18042 decimal digits. There are no more terms <= 2810.

a(9) > 5000. - Michael S. Branicky, Apr 13 2025

Examples

			As primorial(2)^4 + 1 = (3*2)^4 + 1 = 1297 is prime, 2 is a term.
		

Crossrefs

Cf. A002110, A092061.

Extensions

a(1) = 0 inserted by Michael S. Branicky, Apr 13 2025