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 A176867 Least odd number that requires n Collatz (3x+1) iterations to reach 1, or zero if there is no such number. 4
 1, 0, 0, 0, 0, 5, 0, 3, 0, 13, 0, 53, 17, 35, 11, 23, 7, 15, 29, 9, 19, 37, 77, 25, 49, 99, 33, 65, 131, 43, 87, 173, 57, 115, 39, 79, 153, 305, 105, 203, 407, 135, 271, 541, 185, 361, 123, 247, 481, 169, 329, 641, 219, 427, 159, 295, 569, 1139, 379, 759, 283, 505, 1011 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS Both the 3x+1 steps and the halving steps are counted. a(n)=0 only for n = 1, 2, 3, 4, 6, 8, and 10. Sequence A033491 gives the least even or odd number requiring n iterations. LINKS T. D. Noe, Table of n, a(n) for n=0..1924 CROSSREFS Cf. A176866, A176868 Sequence in context: A355068 A261219 A085850 * A351208 A229175 A326188 Adjacent sequences: A176864 A176865 A176866 * A176868 A176869 A176870 KEYWORD nonn AUTHOR T. D. Noe, Apr 27 2010 STATUS approved

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Last modified November 26 14:22 EST 2022. Contains 358362 sequences. (Running on oeis4.)