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A074809 Largest prime factor of A019518, concatenation of first n primes. 3
2, 23, 47, 2357, 223, 35339, 214282847, 7717859, 806801, 185176472401, 357211, 4967701595369, 104364752351, 27558919, 5269410931806332951, 274784055330749, 1191126125288819, 178258515898000387, 2313161253378144566969023310693, 8730041915527145606449758346652473, 26293517701186435480644832888393, 29890227360205834316383307128051, 3858432486690092813, 7122852423207105431971, 93753283248830261744671 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

n=5: concatenation of {2,3,5,7,11} is 235711=7.151.223, largest prime divisor is a(5)=223.

MATHEMATICA

<<NumberTheory`NumberTheoryFunctions` sz[x_] :=FromDigits[Flatten[Table[IntegerDigits[Prime[j]], {j, 1, x}], 1]] Table[Max[PrimeFactorList[sz[w]]], {w, 1, 25}] (Labos)

Table[FactorInteger[FromDigits[Flatten[IntegerDigits/@Prime[ Range[n]]]]][[-1, 1]], {n, 25}] (* Harvey P. Dale, Apr 27 2015 *)

CROSSREFS

Cf. A019158.

Sequence in context: A049592 A054679 A057621 * A084237 A106928 A070934

Adjacent sequences:  A074806 A074807 A074808 * A074810 A074811 A074812

KEYWORD

nonn,base

AUTHOR

Jason Earls, Sep 08 2002

EXTENSIONS

More terms from Labos Elemer, Mar 18 2005

Edited by Charles R Greathouse IV, Apr 23 2010

STATUS

approved

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Last modified November 15 11:18 EST 2019. Contains 329144 sequences. (Running on oeis4.)