



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
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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

Table of n, a(n) for n=0..50.
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



