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 A067139 Irreducible elements in OR-numbral arithmetic. 9
 1, 2, 3, 5, 9, 11, 13, 17, 19, 23, 25, 29, 33, 35, 37, 39, 41, 43, 49, 53, 57, 65, 67, 69, 71, 75, 77, 79, 81, 83, 87, 89, 93, 97, 101, 105, 107, 113, 117, 121, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 157, 159, 161, 163, 167, 169, 171, 177, 179 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that there is no number d in range 1 < d < n with d*k = n for any 1 < k < n, where * is defined in A066376. See A048888 for the definition of OR-numbral arithmetic. Note that 2 is the only prime element in OR-numbral arithmetic; for all other nonunit irreducibles x there exist numbers a and b not divisible by x such that x is a divisor of a * b. Numbers n such that A066376(n) = 1. 1 together with primes in lunar arithmetic base 2. - N. J. A. Sloane, Aug 14 2010 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..500 D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic, arXiv:1107.1130 [math.NT], 2011 [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing] D. Applegate, M. LeBrun, N. J. A. Sloane, Dismal Arithmetic, J. Int. Seq. 14 (2011) # 11.9.8. A. Frosini and S. Rinaldi, On the Sequence A079500 and Its Combinatorial Interpretations, J. Integer Seq., Vol. 9 (2006), Article 06.3.1. PROG (Haskell) import Data.List (elemIndices) a067139 n = a067139_list !! (n-1) a067139_list = 1 : map (+ 1) (elemIndices 1 a066376_list) -- Reinhard Zumkeller, Mar 01 2013 CROSSREFS Cf. A003986, A067138, A048888, A007059. See A169912 for the number of elements that are n bits long - N. J. A. Sloane, Aug 31 2010. See A171000 for the binary expansions. Sequence in context: A290475 A191183 A078645 * A014657 A171056 A161514 Adjacent sequences:  A067136 A067137 A067138 * A067140 A067141 A067142 KEYWORD nonn,nice AUTHOR Jens Voß, Jan 02 2002 EXTENSIONS Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe and Joshua Zucker, Jun 12 2007 STATUS approved

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Last modified May 26 08:39 EDT 2020. Contains 334620 sequences. (Running on oeis4.)