This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A072142 #6 Sep 27 2017 11:47:14 %S A072142 11436678,13973058,19582398,23981958,30581397,32662377,33218856, %T A072142 42464466,44664246,48737106,61936974,69746193,71064873,76226733 %N A072142 Numbers n such that 14 applications of 'Reverse and Subtract' lead to n, whereas fewer than 14 applications do not lead to n. %C A072142 There are 14 eight-digit terms in the sequence. Further terms are obtained (a) by inserting at the center of these terms either any number of 9's (for 11436678, 32662377, 33218856, 76226733) or any number of 0's (for the other ten terms) and (b) by concatenating a term any number of times with itself and inserting an equal number of 0's at all junctures. Method (b) may be applied recursively to all terms. - Revised thanks to a comment from Hans Havermann, Jan 20 2004. %F A072142 n = f^14(n), n <> f^k(n) for k < 14, where f: x -> |x - reverse(x)|. %e A072142 11436678 -> 76226733 -> 42464466 -> 23981958 -> 61936974 -> 13973058 -> 71064873 -> 33218856 -> 32662377 -> 44664246 -> 19582398 -> 69746193 -> 30581397 -> 48737106 -> 11436678. %Y A072142 Cf. A072137, A072140, A072141, A072143, A072718, A072719. %K A072142 base,nonn %O A072142 1,1 %A A072142 _Klaus Brockhaus_, Jun 24 2002