A078554 Largest prime dividing sigma(5,n).

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

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