The On-Line Encyclopedia of Integer Sequences (OEIS)

A060630 revision #4

A060630

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.

0, 1, 10, 19, 109, 149, 197, 399, 694, 796, 893, 897, 1167, 1579, 1596, 1667, 1790, 1777, 2859, 1779, 1778, 1873, 3679, 5926, 11289, 9539, 13551, 4589, 5960, 12066, 12265, 19119, 10927, 12379, 11742, 65220, 34038, 40390, 1110025, 10100023

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OFFSET

0,3

COMMENTS

24-th and 26-th terms are unknown, but a(25)=9539, a(27)=4589, and a(28)=5960.

LINKS

Table of n, a(n) for n=0..39.

FORMULA

a(n)=10^(n-2)+9, for n=2, 3, 4 and for n > 40

EXAMPLE

a(5)=149 because 149 -(1)-> 513 -(2)-> 64 -(3)-> 10 -(4)-> 1 -(5)-> 0. a(7)=399 because 399 -(1)-> 1218 -(2)-> 339 -(3)-> 612 -(4)-> 73 -(5)-> 10 -(6)-> 1 -(7)-> 0.

CROSSREFS

Sequence in context: A219688 A166706 A131495 * A070199 A015445 A220005

Adjacent sequences: A060627 A060628 A060629 * A060631 A060632 A060633

KEYWORD

base,nonn,new

AUTHOR

Jason Earls (jcearls(AT)cableone.net), Apr 14 2001

EXTENSIONS

More terms from Berend Jan van der Zwaag, Jun 23 2001

STATUS

approved