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A138961 a(n) = largest prime divisor of A138957(n). 6
1, 3, 41, 617, 823, 643, 9721, 14593, 3803, 14405693, 10939223, 4156374407, 2663693, 5603770631, 1221751714624799, 287108811653770498027, 74103167823547, 11843077531813991, 726216405947772436185983423, 769725127, 18274551225153265813469 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For smallest prime divisors see A138960.

LINKS

Robert Price, Table of n, a(n) for n = 1..60

MATHEMATICA

a = {}; b = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[Length[w] - k + 1]]], {k, 1, Length[w]}]; p = FromDigits[a]; AppendTo[b, First[Last[FactorInteger[p]]]], {n, 1, 18}]; b

A137957[n_] := FromDigits[Flatten[Reverse /@ IntegerDigits[Range[n]]]];

Table[First[Last[FactorInteger[A137957[n]]]], {n, 39}] (* Robert Price, May 10 2019 *)

CROSSREFS

Cf. A104759, A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138958, A138960.

Sequence in context: A189356 A155672 A073844 * A075022 A300281 A012175

Adjacent sequences:  A138958 A138959 A138960 * A138962 A138963 A138964

KEYWORD

nonn,base

AUTHOR

Artur Jasinski, Apr 04 2008

STATUS

approved

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Last modified July 18 15:26 EDT 2019. Contains 325143 sequences. (Running on oeis4.)