A109891 Least number that requires n steps to reach 0 by repeated application of f: x -> abs(x - reverse(x)).

0, 1, 10, 16, 14, 15, 13, 1011, 1017, 1037, 1027, 1014, 1013, 1028, 100143, 100135, 100145, 100134, 100103, 100195, 100137, 100227, 100114, 100128, 100194, 100107, 100307, 100277, 100413, 100345, 100429, 100215, 100444, 100237, 100433, 100335

Offset: 0

Author

Amarnath Murthy, Jul 13 2005

Keywords

• base
• nonn

Comments

Coincides with A072138 for the first 14 and many later terms.

Examples

			f(16) = 61-16 = 45, f(45) = 54-45 = 9, f(9) = 9-9 = 0. For no k < 16 exactly three steps lead to 0, hence a(3) = 16.
		

Crossrefs

Cf. A072137, A072138, A072141.

Extensions

Edited, corrected and extended by Klaus Brockhaus, Jul 14 2005