A066590 Numbers which can be expressed as product of a number and its reversal in at least three different ways.

635040, 1015560, 1446480, 1854720, 4356000, 6350400, 10155600, 14464800, 18547200, 43560000, 51665040, 59552640, 63504000, 67944240, 76839840, 78127560, 82623060, 88560360, 95236960, 99497160, 101556000, 105094080

Offset: 1

Author

Robert G. Wilson v, Jan 08 2002

Keywords

• nonn

Comments

A066598 is a subsequence, e.g., a(2)=A066598(1). - M. F. Hasler, Feb 14 2012

Examples

			63540 = 1440 * 411 = 2520 * 252 = 4410 * 144.
		

Links

• Shyam Sunder Gupta, Equal Product of Reversible Numbers (EPRN), Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 12, 353-365.

Crossrefs

Cf. A066531, A066598.

Programs

Mathematica

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 ]] & ]]]

Extensions

Definition clarified by M. F. Hasler, Feb 14 2012

Definition corrected by N. J. A. Sloane, Aug 01 2019