A094486 Primes of form 2^j + 223^j.

2, 2472973457, 6115597639891380737

Offset

1,1

Comments

Expression 2^j + q^j below q = prime <= prime[130] provided always prime at j=0; or for j=1 if q is a lesser-twin-prime; or more rarely 3 or 4 primes [four ones at q=3,5,17,37,59,137,179,223,461]; never found 5 or more relevant primes and the corresponding exponents proved to be powers of 2. Formal proofs of observations wanted.

See comment by Michael Somos, Aug 27 2004 for proof that j must be zero or a power of 2. - Robert Price, Apr 30 2013

Since the number j must be zero or a power of 2, checked j being powers of two through 2^19. Thus a(5) > 10^2400000. Primes of this magnitude are rare (about 1 in 5.6 million), so chance of finding one is remote with today's computer algorithms and speeds. - Robert Price, Apr 30 2013

Links

Table of n, a(n) for n=1..3.

Example

The relevant exponents are powers of 2: 0,4,8,128. a(4) = 2^128 + 223^128 = 382844.....1067137 (a prime with 301 decimal digits).

Crossrefs

Cf. A082101, A094473-A094485.

Sequence in context: A325175 A306499 A051241 * A109741 A105759 A154422

Adjacent sequences: A094483 A094484 A094485 * A094487 A094488 A094489

Keyword

nonn,bref

Author

Labos Elemer, Jun 01 2004

Extensions

Corrected by T. D. Noe, Nov 15 2006

Status

approved