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Search: id:A075022
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| A075022 |
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a(1) = 1; for n>1, a(n) = the largest prime divisor of the number C(n) formed from the concatenation of 1,2,3,... up to n. |
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+0
8
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| 1, 3, 41, 617, 823, 643, 9721, 14593, 3803, 1234567891, 630803, 2110805449, 869211457, 205761315168520219, 8230452606740808761, 1231026625769, 584538396786764503, 801309546900123763, 833929457045867563
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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Zak Seidov, Table of n, a(n) for n = 1..50.
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EXAMPLE
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a(4) = 617 since 1234 = 2*617.
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MATHEMATICA
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a = {}; b = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[k]]], {k, 1, Length[w]}]; p = FromDigits[a]; AppendTo[b, First[Last[FactorInteger[p]]]], {n, 1, 25}]; b - Artur Jasinski (grafix(AT)csl.pl), Apr 04 2008
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CROSSREFS
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Cf. A075019, A075020, A075021.
Cf. A104759, A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138958, A138959, A138960, A138961, A138962.
Adjacent sequences: A075019 A075020 A075021 this_sequence A075023 A075024 A075025
Sequence in context: A087544 A073844 A138961 this_sequence A012175 A007313 A012053
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 01 2002
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EXTENSIONS
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More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 03 2003
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