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 A127933 A006577(k), k = pure hailstone numbers from A061641. 0
 0, 0, 7, 8, 16, 19, 9, 17, 20, 20, 7, 10, 23, 111, 18, 26, 21, 21, 34, 8, 29, 16, 11, 24, 112, 112, 32, 19, 107, 27, 14, 22, 115, 14, 35, 35, 22, 9, 30, 17, 17, 12, 118, 25, 25, 38, 113, 113, 69, 33, 33 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Impure hailstone numbers are those which occur in the trajectories of smaller numbers. Thus 5 is impure since it occurs in the trajectory of 3. LINKS Douglas J. Shaw, The Pure Numbers Generated by the Collatz Sequence, The Fibonacci Quarterly, Vol. 44, Number 3, August 2006, p. 194. FORMULA a(n) = A006577(k), where k = the pure hailstone numbers from A061641 EXAMPLE A061641 (pure hailstone numbers) = 0, 1, 3, 6, 7, 9, 12...; as k in A006577(k), which gives the numbers of iterative steps: 0, 0, 7, 8, 16, 19, 9,... For "3" the trajectory has 7 terms: (10, 5, 16, 8, 4, 2, 1). CROSSREFS Cf. A006577, A061641. Sequence in context: A093083 A125195 A099534 * A006878 A022312 A055661 Adjacent sequences:  A127930 A127931 A127932 * A127934 A127935 A127936 KEYWORD nonn AUTHOR Gary W. Adamson, Feb 08 2007 STATUS approved

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