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A097154 Number of iterations of f(x) = reverse(x) - maxdigit(x) needed to reach zero, or -1 if zero is never reached, where maxdig(n) is the largest digit of n. 5
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 4, 4, 5, 3, 3, 3, 3, 1, 2, 2, 4, 4, 6, 5, 3, 3, 3, 1, 2, 2, 2, 4, 4, 7, 3, 3, 3, 1, 2, 2, 2, 2, 4, 4, 5, 3, 3, 1, 2, 2, 2, 2, 2, 4, 6, 3, 3, 1, 2, 2, 2, 2, 2, 2, 4, 5, 3, 1, 2, 2, 2, 2, 2, 2, 2, 4, 3, 1, 2, 2, 2, 2, 2, 2, 2, 2, -1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 6, 6, 9, 7, 8, 8, 10, 7, 2, 3, 10, 7, 8, 9, 3, 3, 3, 3, 4, 4, 4, 4, 4, 8, 4, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,11

COMMENTS

a(89)=-1 because 89 is the first number that will not reach zero: 98-9=89. It is conjectured that 0 and 89 are the only fixed points of f. See A097155 for numbers that reach 89.

LINKS

Table of n, a(n) for n=1..127.

EXAMPLE

a(12)=4 because 12 -> 19 -> 82 -> 20 -> 0.

CROSSREFS

Cf. A097153, A097155, A097156, A097157, A097158.

Sequence in context: A236680 A162798 A088650 * A108421 A104058 A132345

Adjacent sequences:  A097151 A097152 A097153 * A097155 A097156 A097157

KEYWORD

base,easy,sign

AUTHOR

Jason Earls, Aug 01 2004

STATUS

approved

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Last modified June 25 10:28 EDT 2021. Contains 345453 sequences. (Running on oeis4.)