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A346014 Numbers whose average number of distinct prime factors of their divisors is an integer. 3

%I #8 Jul 02 2021 03:49:36

%S 1,6,10,14,15,21,22,26,33,34,35,38,39,46,51,55,57,58,62,65,69,74,77,

%T 82,85,86,87,91,93,94,95,106,111,115,118,119,122,123,129,133,134,141,

%U 142,143,145,146,155,158,159,161,166,177,178,183,185,187,194,201,202

%N Numbers whose average number of distinct prime factors of their divisors is an integer.

%C First differs from A030229 at n = 275. a(275) = 900 is the least term that is not squarefree and therefore not in A030229.

%C The least term whose exponents in its prime factorization are not all the same is 1080 = 2^3 * 3^3 * 5.

%C The least term whose exponents in its prime factorization are distinct is 1440 = 2^5 * 3^2 * 5.

%C Numbers k such that A000005(k) | A062799(k).

%C Numbers k such that A346010(k) = 1.

%C Numbers k such that if the prime factorization of k is Product_{i} p_i^e_i, then Sum_{i} e_i/(e_i + 1) is an integer.

%C Includes all the squarefree numbers with an even number of prime divisors (A030229), i.e., the union of A006881, A046386, A067885, A123322, ...

%C If k is squarefree with m prime divisors then k^(m-1) is a term. E.g., the squares of the sphenic numbers (A162143) are terms.

%H Amiram Eldar, <a href="/A346014/b346014.txt">Table of n, a(n) for n = 1..10000</a>

%e 6 is a term since it has 4 divisors, 1, 2, 3 and 6 and (omega(1) + omega(2) + omega(3) + omega(6))/4 = (0 + 1 + 1 + 2)/4 = 1 is an integer.

%t f[p_, e_] := e/(e + 1); d[1] = 1; d[n_] := Denominator[Plus @@ f @@@ FactorInteger[n]]; Select[Range[200], d[#] == 1 &]

%Y Cf. A000005, A001221, A062799, A346009, A346010.

%Y Subsequences: A006881, A030229, A046386, A067885, A123322, A162143.

%K nonn

%O 1,2

%A _Amiram Eldar_, Jul 01 2021

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Last modified May 8 19:26 EDT 2024. Contains 372341 sequences. (Running on oeis4.)