A347246 a(n) = 1 if the greatest prime factor of A000593(n) [sum of odd divisors of n] is at least as large as the greatest prime factor of n itself, otherwise a(n) = 0.

1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Index entries for sequences related to sigma(n)

Formula

a(n) = [A006530(A000593(n)) >= A006530(n)], where [ ] is the Iverson bracket.

For n > 1, a(n) = 1 iff A347245(n) = 1.

Mathematica

A347246[n_] := Boole[FactorInteger[DivisorSum[n, # &, OddQ]][[-1, 1]] >= FactorInteger[n][[-1, 1]]];
Array[A347246, 100] (* Paolo Xausa, Jan 01 2026 *)

Prog

(PARI)
A006530(n) = if(1==n, n, my(f=factor(n)); f[#f~, 1]);
A000265(n) = (n >> valuation(n, 2));
A000593(n) = sigma(A000265(n));
A347246(n) = (A006530(A000593(n))>=A006530(n));

Crossrefs

Characteristic function of A347247. A347248 gives the positions of zeros.

Cf. A000593, A006530, A347244, A347245.

Cf. also A336352.

Sequence in context: A326499 A379678 A104124 * A052434 A369034 A015241

Adjacent sequences: A347243 A347244 A347245 * A347247 A347248 A347249

Keyword

nonn

Author

Antti Karttunen, Aug 28 2021

Status

approved