A078551 Largest prime dividing sigma(2,n).

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

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