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 A066599 a(n) = smallest number which can be expressed as the product of a number and its reversal in exactly n different ways. 0
 1, 2520, 635040, 1015560, 10119126106147652568, 11158922880, 5918858243794044864, 1046458990080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(6) = 11158922880 and a(8) = 1046458990080. a(10) = 101191261061476525680, a(12) = 62624600899319949840, a(14) = 59188582437940448640. - Chai Wah Wu, Apr 16 2019 LINKS 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. From Chai Wah Wu, Apr 16 2019: (Start) a(5) = 10119126106147652568 = 8848263411 * 1143628488 = 8044687521 * 1257864408 = 4884561702 * 2071654884 = 4440958722 * 2278590444 = 4082378742 * 2478732804 a(7) = 5918858243794044864 = 4834624221 * 1224264384 = 4439423331 * 1333249344 = 4036246641 * 1466426304 = 2762642412 * 2142462672 = 2566246032 * 2306426652 = 2536813332 * 2333186352 = 2511746532 * 2356471152 a(10) = 101191261061476525680 = 88482634110 * 1143628488 = 80446875210 * 1257864408 = 48845617020 * 2071654884 = 44409587220 * 2278590444 = 40823787420 * 2478732804 = 24787328040 * 4082378742 = 22785904440 * 4440958722 = 20716548840 * 4884561702 = 12578644080 * 8044687521 = 11436284880 * 8848263411 a(12) = 62624600899319949840 = 46891553310 * 1335519864 = 46055795310 * 1359755064 = 42632986410 * 1468923624 = 28946436120 * 2163464982 = 26795173320 * 2337159762 = 26317597320 * 2379571362 = 23795713620 * 2631759732 = 23371597620 * 2679517332 = 21634649820 * 2894643612 = 14689236240 * 4263298641 = 13597550640 * 4605579531 = 13355198640 * 4689155331 a(14) = 59188582437940448640 = 48346242210 * 1224264384 = 44394233310 * 1333249344 = 40362466410 * 1466426304 = 27626424120 * 2142462672 = 25662460320 * 2306426652 = 25368133320 * 2333186352 = 25117465320 * 2356471152 = 23564711520 * 2511746532 = 23331863520 * 2536813332 = 23064266520 * 2566246032 = 21424626720 * 2762642412 = 14664263040 * 4036246641 = 13332493440 * 4439423331 = 12242643840 * 4834624221 (End) 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 A282433 Adjacent sequences:  A066596 A066597 A066598 * A066600 A066601 A066602 KEYWORD nonn AUTHOR Robert G. Wilson v, Jan 08 2002 EXTENSIONS a(5) and a(7) from Chai Wah Wu, Apr 16 2019 Definition corrected by N. J. A. Sloane, Aug 01 2019 STATUS approved

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Last modified July 1 06:25 EDT 2022. Contains 354952 sequences. (Running on oeis4.)