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

1,1

Comments

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

Links

Table of n, a(n) for n=1..22.

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

Example

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

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 ]] & ]]]

Crossrefs

Cf. A066531, A066598.

Sequence in context: A183678 A267362 A251564 * A237909 A185476 A237903

Adjacent sequences: A066587 A066588 A066589 * A066591 A066592 A066593

Keyword

nonn,changed

Author

Robert G. Wilson v, Jan 08 2002

Extensions

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

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

Status

approved