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Numbers n such that 7 applications of 'Reverse and Subtract' lead to n, whereas fewer than 7 applications do not lead to n.
10

%I #16 Jan 05 2025 19:51:41

%S 142710354353443018141857289645646556981858,

%T 236547461211163745741763452538788836254258,

%U 331948602685207939133668051397314792060866,336111694728585211732663888305271414788267

%N Numbers n such that 7 applications of 'Reverse and Subtract' lead to n, whereas fewer than 7 applications do not lead to n.

%C There are 7 forty-two-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.

%H Ray Chandler, <a href="/A292856/b292856.txt">Table of n, a(n) for n = 1..7</a>

%H J. H. E. Cohn, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Scanned/28-2/cohn.pdf">Palindromic differences</a>, Fibonacci Quart. 28 (1990), no. 2, 113-120.

%F n = f^7(n), n <> f^k(n) for k < 7, where f: x -> |x - reverse(x)|.

%e 142710354353443018141857289645646556981858 -> 715479301293103964616284520698706896035383 -> 331948602685207939133668051397314792060866 -> 336111694728585211732663888305271414788267 -> 426775719443918676633573224280556081323366 -> 236547461211163745741763452538788836254258 -> 615905177676671508625384094822323328491374 -> 142710354353443018141857289645646556981858

%Y Cf. A072142, A072143, A072718, A072719, A215669, A292634, A292635, A292846, A292857, A292858, A292859.

%K nonn,base

%O 1,1

%A _Meritxell Vila MiƱana_, Sep 25 2017

%E Terms ordered by _Ray Chandler_, Sep 27 2017