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 A099439 Numbers k such that A000295(k) = 2^k-k-1 is prime. 5
 4, 10, 14, 16, 26, 50, 56, 70, 116, 2072, 6250, 13670, 14216, 14626, 396128 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The next term is > 400000. Equals A063791 + 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008 Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 14 2019 LINKS EXAMPLE a(1) = 4 because 2^4 - 4 - 1 = 11 is prime. CROSSREFS Cf. A000295 (2^n-n-1), A099440 (primes in A000295), A099441 (2^n-n-1 is a semiprime), A099442 (semiprimes in A000295). Sequence in context: A310361 A310362 A310363 * A310364 A310365 A310366 Adjacent sequences:  A099436 A099437 A099438 * A099440 A099441 A099442 KEYWORD nonn,more,hard AUTHOR Hugo Pfoertner, Oct 18 2004 EXTENSIONS a(15) (a PRP) from Karsten Bonath, Jun 07 2018 STATUS approved

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Last modified May 26 17:16 EDT 2022. Contains 354092 sequences. (Running on oeis4.)