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 A094486 Primes of form 2^j + 223^j. 1
 2, 2472973457, 6115597639891380737 (list; graph; refs; listen; history; text; internal format)
 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 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

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Last modified August 4 06:22 EDT 2020. Contains 336201 sequences. (Running on oeis4.)