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#12 by N. J. A. Sloane at Thu Aug 13 14:01:06 EDT 2020
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Erich Friedman, <a href="httphttps://wwwerich-friedman.stetsongithub.edu/~efriedmaio/mathmagic/0200.html">Problem of the Month (Feb 2000)</a>
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Discussion
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| Thu Aug 13
| 14:01
| OEIS Server: https://oeis.org/edit/global/2865
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#11 by N. J. A. Sloane at Fri Dec 15 17:34:59 EST 2017
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_Jason Earls (zevi_35711(AT)yahoo.com), _, Apr 14 2001
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Discussion
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| Fri Dec 15
| 17:34
| OEIS Server: https://oeis.org/edit/global/2722
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#10 by Jon E. Schoenfield at Fri Mar 13 00:31:05 EDT 2015
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#9 by Jon E. Schoenfield at Fri Mar 13 00:31:03 EDT 2015
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24-th24th and 26-th26th terms are unknown, but a(25)=9539, a(27)=4589 and a(28)=5960.
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a(n)=10^(n-2)+9, for n=2, 3, 4 and for n > 40.
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| STATUS
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approved
editing
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#8 by N. J. A. Sloane at Wed Aug 24 00:39:08 EDT 2011
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#7 by N. J. A. Sloane at Wed Aug 24 00:39:03 EDT 2011
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For n > 9 let f(n) be formed by writing down the sums of every pair of consecutive digits of n: e.g. f(3469)=71015 because 3+4=7,4+6=10,6+9=15; let f(n)=0 if n is a single digit. Sequence gives smallest number requiring n iterations to reach zero.
a(n) gives smallest number requiring n iterations of the map i -> A053392(i) to reach zero.
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Cf. A053392.
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approved
editing
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#6 by N. J. A. Sloane at Fri Feb 27 03:00:00 EST 2009
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| COMMENTS
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24-th and 26-th terms are unknown, but a(25)=9539, a(27)=4589, and a(28)=5960.
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| KEYWORD
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base,nonn,new
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#5 by N. J. A. Sloane at Fri Jan 09 03:00:00 EST 2009
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Erich Friedman, <a href="http://www.stetson.edu/~efriedma/mathmagic/0200.html">Problem of the Month (Feb 2000)</a>
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| KEYWORD
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base,nonn,new
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| AUTHOR
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Jason Earls (jcearlszevi_35711(AT)cableoneyahoo.netcom), Apr 14 2001
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#4 by N. J. A. Sloane at Fri Feb 24 03:00:00 EST 2006
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| FORMULA
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a(n)=10^(n-2)+9, for n=2,, 3,, 4 and for n > 40
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base,nonn,new
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#3 by N. J. A. Sloane at Wed Sep 22 03:00:00 EDT 2004
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base,nonn,new
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| AUTHOR
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Jason Earls (jcearls(AT)4grccableone.comnet), Apr 14 2001
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