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 A335978 #32 Sep 24 2021 22:03:57 %S A335978 0,9,18,27,36,45,54,63,72,81,90,99,180,189,198,270,279,297,360,369, %T A335978 396,450,459,495,540,549,594,630,639,693,720,729,792,810,819,891,900, %U A335978 909,990,999,1089,1179,1188,1269,1278,1359,1368,1449,1458,1539,1548,1629,1638,1719,1728,1800,1809,1818,1890,1908,1980,1989,1998,2079 %N A335978 Numbers m of the form abs(k - reverse(k)) for at least one k. %C A335978 All terms are divisible by 9. %C A335978 Let f(k) = k - reverse(k). Then f(reverse(k)) = -f(k), since f(reverse(k)) = reverse(k) - reverse(reverse(k)) = reverse(k) - k = - (k - reverse(k)) = -f(k). %C A335978 Iteration of the function f(k) = k - reverse(k) leads to A072140, A072141, A072142, and A072143. %H A335978 Michael P. Greaney, <a href="https://plus.maths.org/content/arithmetic-made-easy-reversible-numbers">Remarkable Reversible Numbers</a>, +plus magazine, (September 29, 2015). %Y A335978 Cf. A056965, A067030, A072140, A072141, A072142, A072143. %Y A335978 Dividing by 9 gives A334145. %K A335978 nonn,base %O A335978 1,2 %A A335978 _Michael Greaney_, Jul 03 2020