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 A109840 Largest prime factor of the reverse concatenation of the first n consecutive odd numbers. 1
 31, 59, 443, 13933, 2609, 83089, 18937669, 57697, 71615663503, 161768817795401, 4356390089, 4668342004597, 109230695824219, 2770122504473483, 217596035578054625221, 1721572826917, 659160492491 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE n = 6: a(6) = 83089 because 131197531 = 1579 * 83089. MATHEMATICA s=1; ss={}; Do[news=FromDigits[Flatten[{IntegerDigits[n], IntegerDigits[s]}]]; fi=FactorInteger[news][[ -1, 1]]; s=news; AppendTo[ss, fi], {n, 3, 60, 2}]; A109840=ss CROSSREFS Cf. A109837 = smallest prime factor of the reverse concatenation of the first n consecutive odd numbers. Sequence in context: A327447 A139954 A153636 * A108293 A316349 A063339 Adjacent sequences: A109837 A109838 A109839 * A109841 A109842 A109843 KEYWORD base,nonn AUTHOR Zak Seidov, Jul 05 2005 STATUS approved

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Last modified March 22 17:23 EDT 2023. Contains 361432 sequences. (Running on oeis4.)