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A292634
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Numbers n such that 4 iterations of 'Reverse and Subtract' lead to n, whereas fewer than 4 iterations do not lead to n.
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9
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OFFSET
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1,1
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COMMENTS
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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.
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LINKS
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FORMULA
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n = f^4(n), n <> f^k(n) for k < 4, where f: x -> |x - reverse(x)|.
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EXAMPLE
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|169140971830859028 - 820958038179041961| = 651817066348182933
|651817066348182933 - 339281843660718156| = 312535222687464777
|312535222687464777 - 777464786222535213| = 464929563535070436
|464929563535070436 - 634070535365929464| = 169140971830859028
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CROSSREFS
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Cf. A072142, A072143, A072718, A072719, A215669, A292635, A292846, A292856, A292857, A292858, A292859.
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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