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A066590
Numbers which can be expressed as product of a number and its reversal in at least three different ways.
0
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
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
Sequence in context: A183678 A267362 A251564 * A237909 A185476 A237903
KEYWORD
nonn
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