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%I #9 Jan 05 2025 19:51:41
%S 1195005230033599502088049947699664004979,
%T 1381092199992389193086189078000076108069,
%U 1417996648846699605185820033511533003948,2845548027720844548271544519722791554517
%N Numbers n such that 13 applications of 'Reverse and Subtract' lead to n, whereas fewer than 13 applications do not lead to n.
%C There are 13 forty-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="/A292992/b292992.txt">Table of n, a(n) for n = 1..13</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^13(n), n <> f^k(n) for k < 13, where f: x -> |x - reverse(x)|.
%e 1195005230033599502088049947699664004979 -> 8598999439933899906714010005600661000932 -> 6208997779868899802537910022201311001974 -> 1417996648846699605185820033511533003948 -> 7075006702306600680629249932976933993193 -> 3161013305514201251368389866944857987486 -> 3686884278982488587263131157210175114127 -> 3527231431145022726364727685688549772736 -> 2845548027720844548271544519722791554517 -> 4309003944558309903456909960554416900965 -> 1381092199992389193086189078000076108069 -> 8226924500016320623717730754999836793762 -> 5552948110021750246544470518899782497534 ->
%e 1195005230033599502088049947699664004979.
%Y Cf. A072142, A072143, A072718, A072719, A215669, A292634, A292635, A292846, A292856, A292857, A292858, A292859, A292993.
%K nonn,base
%O 1,1
%A _Ray Chandler_, Sep 28 2017