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A066599 Least n-EPRNs (Equal Product Of Reversible Numbers): numbers which can be expressed as the product of two reversible numbers in just n different ways. 0
1, 2520, 635040, 1015560 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

a(6) = 11158922880 and a(8) = 1046458990080.

EXAMPLE

a(1) = 1 = 1*1; a(2) = 2520 = 120*21 = 210*12; a(3) = 635040 = 1440*441 = 2520*252 = 4410*144; a(4) = 1015560 = 1560*651 = 2730*372 = 3720*273 = 6510*156; a(6) = 11158922880 = 132480*84231 = 231840*48132 = 275040*40572 = 405720*27504 = 481320*23184 = 842310*13248; a(8) = 1236480*846321 = 2163840*483612 = 2329440*449232 = 2567040*407652 = 4076520*256704 = 4492320*232944 = 4836120*216384 = 8463210*123648.

MATHEMATICA

f[n_] := (m = ToExpression[StringReverse[ToString[n]]]; If[n >= m, n*m, 0]); a = Sort[Table[f[n], {n, 0, 10^7}]]; While[a[[1]] == 0, a = Drop[a, 1]]; Do[k = 1; While[ a[[k]] != a[[k + n - 1]], k++ ]; Print[ a[[k]]], {n, 1, 4} ]

CROSSREFS

Cf. A066531.

Sequence in context: A064592 A179722 A109480 * A107531 A123485 A172553

Adjacent sequences:  A066596 A066597 A066598 * A066600 A066601 A066602

KEYWORD

nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 08 2002

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Last modified February 13 20:37 EST 2012. Contains 205554 sequences.