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A078554 Largest prime dividing sigma(5,n). 1
11, 61, 151, 521, 61, 191, 41, 4561, 521, 13421, 151, 2411, 191, 521, 1801, 101, 4561, 2251, 521, 191, 13421, 211, 61, 1741, 2411, 1181, 191, 401, 521, 21821, 331, 13421, 101, 521, 4561, 1824841, 2251, 2411, 521, 4111, 191, 3341101, 13421, 4561, 211 (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(A001160(n)).

EXAMPLE

Observe nontrivial frequent occurrence of several primes like 61,191,521,4561, etc.

MATHEMATICA

gpf[n_] := FactorInteger[n][[-1, 1]]; a[n_] := gpf[DivisorSigma[5, n]]; Array[a, 50, 2] (* Amiram Eldar, Aug 01 2019 *)

CROSSREFS

Cf. A006530, A001157-A001160, A071190.

Sequence in context: A106993 A066597 A199326 * A189227 A002650 A060884

Adjacent sequences:  A078551 A078552 A078553 * A078555 A078556 A078557

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 05 2002

STATUS

approved

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Last modified September 15 04:09 EDT 2019. Contains 327062 sequences. (Running on oeis4.)