A292634 Numbers n such that 4 iterations of 'Reverse and Subtract' lead to n, whereas fewer than 4 iterations do not lead to n.

169140971830859028, 312535222687464777, 464929563535070436, 651817066348182933

Offset: 1

Author

Meritxell Vila Miñana, Sep 20 2017

Keywords

• nonn
• base
• more

Comments

There are 4 eighteen-digit terms in the sequence. Terms of derived sequences can be obtained either by inserting at the center of their digits any number of 9's or by concatenating a term any number of times with itself and inserting an equal number of 0's at all junctures.

Examples

			|169140971830859028 - 820958038179041961| = 651817066348182933
|651817066348182933 - 339281843660718156| = 312535222687464777
|312535222687464777 - 777464786222535213| = 464929563535070436
|464929563535070436 - 634070535365929464| = 169140971830859028
		

Links

• J. H. E. Cohn, Palindromic differences, Fibonacci Quart. 28 (1990), no. 2, 113-120.

Crossrefs

Cf. A072142, A072143, A072718, A072719, A215669, A292635, A292846, A292856, A292857, A292858, A292859.

Formula

n = f^4(n), n <> f^k(n) for k < 4, where f: x -> |x - reverse(x)|.

Extensions

Terms ordered by Ray Chandler, Sep 27 2017