A060630 a(n) gives smallest number requiring n iterations of the map i -> A053392(i) 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

Offset

0,3

Comments

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

Links

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

Erich Friedman, Problem of the Month (Feb 2000)

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

Cf. A053392.

Sequence in context: A219688 A166706 A131495 * A070199 A015445 A220005

Adjacent sequences: A060627 A060628 A060629 * A060631 A060632 A060633

Keyword

base,nonn

Author

Jason Earls, Apr 14 2001

Extensions

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

Status

approved