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

Author

Jason Earls, Apr 14 2001

Keywords

• base
• nonn

Comments

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

Examples

			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.
		

Links

• Erich Friedman, Problem of the Month (Feb 2000)

Crossrefs

Cf. A053392.

Formula

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

Extensions

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