A346556 8-Sondow numbers: numbers k such that p^s divides k/p + 8 for every prime power divisor p^s of k.

1, 3, 16, 48, 336, 14448, 376464, 17716019376, 419963172816

Offset

1,2

Comments

Numbers k such that A235137(k) == 8 (mod k).

A positive integer k is a 8-Sondow number if satisfies any of the following equivalent properties:

1) p^s divides k/p + 8 for every prime power divisor p^s of k.

2) 8/k + Sum_{prime p|k} 1/p is an integer.

3) 8 + Sum_{prime p|k} k/p == 0 (mod k).

4) Sum_{i=1..k} i^phi(k) == 8 (mod k).

Other numbers in the sequence: 17716019376, 419963172816, 67923372668477507285654170088688

Links

Table of n, a(n) for n=1..9.

Github, Jonathan Sondow (1943 - 2020)

J. M. Grau, A. M. Oller-Marcén and D. Sadornil, On µ-Sondow Numbers, arXiv:2111.14211 [math.NT], 2021.

J. M. Grau, A. M. Oller-Marcen and J. Sondow, On the congruence 1^n + 2^n + ... + n^n = d (mod n), where d divides n, arXiv:1309.7941 [math.NT], 2013-2014.

Mathematica

Sondow[mu_][n_]:=Sondow[mu][n]=Module[{fa=FactorInteger[n]}, IntegerQ[mu/n+Sum[1/fa[[i, 1]], {i, Length[fa]}]]]
Select[Range[400000], Sondow[8][#]&]

Crossrefs

Cf. A054377, A007850, A235137, A348058, A348059.

(-1) and (-2) -Sondow numbers: A326715, A330069.

1-Sondow to 9-Sondow numbers: A349193, A330068, A346551, A346552, A346553, A346554, A346555, this sequence, A346557.

Sequence in context: A362007 A212564 A222843 * A004320 A089363 A000574

Adjacent sequences: A346553 A346554 A346555 * A346557 A346558 A346559

Keyword

nonn,more

Author

José María Grau Ribas, Feb 04 2022

Extensions

a(8)-a(9) verified by Martin Ehrenstein, Feb 04 2022

Status

approved