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A078551 Largest prime dividing sigma(2,n). 1
5, 5, 7, 13, 5, 5, 17, 13, 13, 61, 7, 17, 5, 13, 31, 29, 13, 181, 13, 5, 61, 53, 17, 31, 17, 41, 7, 421, 13, 37, 13, 61, 29, 13, 13, 137, 181, 17, 17, 29, 5, 37, 61, 13, 53, 17, 31, 43, 31, 29, 17, 281, 41, 61, 17, 181, 421, 1741, 13, 1861, 37, 13, 127, 17, 61, 449, 29, 53 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 2..10000

FORMULA

a(n) = A006530(A001157(n)).

MATHEMATICA

gpf[n_] := FactorInteger[n][[-1, 1]]; a[n_] := gpf[DivisorSigma[2, n]]; Array[a, 70, 2] (* Amiram Eldar, Aug 01 2019 *)

CROSSREFS

Cf. A006530, A001157-A001160, A071190.

Sequence in context: A097996 A033300 A134130 * A247877 A252006 A158299

Adjacent sequences:  A078548 A078549 A078550 * A078552 A078553 A078554

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 05 2002

STATUS

approved

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Last modified November 16 20:13 EST 2019. Contains 329206 sequences. (Running on oeis4.)