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%I #11 Oct 30 2023 09:53:04
%S 635040,1015560,1446480,1854720,4356000,6350400,10155600,14464800,
%T 18547200,43560000,51665040,59552640,63504000,67944240,76839840,
%U 78127560,82623060,88560360,95236960,99497160,101556000,105094080
%N Numbers which can be expressed as product of a number and its reversal in at least three different ways.
%C A066598 is a subsequence, e.g., a(2)=A066598(1). - _M. F. Hasler_, Feb 14 2012
%e 63540 = 1440 * 411 = 2520 * 252 = 4410 * 144.
%t f[n_] := (m = ToExpression[StringReverse[ToString[n]]]; If[n > m, n*m, 0]); a = Sort[ Table[ f[n], {n, 0, 10^6}]]; While[ a[[1]] == 0, a = Drop[a, 1]]; a[[ Select[ Range[ Length[a]] - 2, a[[ # ]] == a[[ # + 2 ]] & ]]]
%Y Cf. A066531, A066598.
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 08 2002
%E Definition clarified by _M. F. Hasler_, Feb 14 2012
%E Definition corrected by _N. J. A. Sloane_, Aug 01 2019