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 A066590 #14 Mar 14 2025 20:04:03
%S A066590 635040,1015560,1446480,1854720,4356000,6350400,10155600,14464800,
%T A066590 18547200,43560000,51665040,59552640,63504000,67944240,76839840,
%U A066590 78127560,82623060,88560360,95236960,99497160,101556000,105094080
%N A066590 Numbers which can be expressed as product of a number and its reversal in at least three different ways.
%C A066590 A066598 is a subsequence, e.g., a(2)=A066598(1). - _M. F. Hasler_, Feb 14 2012
%H A066590 Shyam Sunder Gupta, <a href="https://doi.org/10.1007/978-981-97-2465-9_12">Equal Product of Reversible Numbers (EPRN)</a>, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 12, 353-365.
%e A066590 63540 = 1440 * 411 = 2520 * 252 = 4410 * 144.
%t A066590 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 A066590 Cf. A066531, A066598.
%K A066590 nonn
%O A066590 1,1
%A A066590 _Robert G. Wilson v_, Jan 08 2002
%E A066590 Definition clarified by _M. F. Hasler_, Feb 14 2012
%E A066590 Definition corrected by _N. J. A. Sloane_, Aug 01 2019