|
| |
|
|
A075022
|
|
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.
|
|
8
| |
|
|
1, 3, 41, 617, 823, 643, 9721, 14593, 3803, 1234567891, 630803, 2110805449, 869211457, 205761315168520219, 8230452606740808761, 1231026625769, 584538396786764503, 801309546900123763, 833929457045867563
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
LINKS
| Zak Seidov, Table of n, a(n) for n = 1..50.
|
|
|
EXAMPLE
| a(4) = 617 since 1234 = 2*617.
|
|
|
MATHEMATICA
| 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
|
|
|
CROSSREFS
| Cf. A075019, A075020, A075021.
Cf. A104759, A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138958, A138959, A138960, A138961, A138962.
Sequence in context: A155672 A073844 A138961 * A012175 A007313 A181675
Adjacent sequences: A075019 A075020 A075021 * A075023 A075024 A075025
|
|
|
KEYWORD
| base,nonn
|
|
|
AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 01 2002
|
|
|
EXTENSIONS
| More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 03 2003
|
| |
|
|
