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%I #32 Sep 24 2021 22:03:57
%S 0,9,18,27,36,45,54,63,72,81,90,99,180,189,198,270,279,297,360,369,
%T 396,450,459,495,540,549,594,630,639,693,720,729,792,810,819,891,900,
%U 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 Numbers m of the form abs(k - reverse(k)) for at least one k.
%C All terms are divisible by 9.
%C 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 Iteration of the function f(k) = k - reverse(k) leads to A072140, A072141, A072142, and A072143.
%H 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 Cf. A056965, A067030, A072140, A072141, A072142, A072143.
%Y Dividing by 9 gives A334145.
%K nonn,base
%O 1,2
%A _Michael Greaney_, Jul 03 2020
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