A157846 -id:A157846 - cp's OEIS frontend

A157847 Numbers which are not a mean of divisors of some arithmetic number A003601(k).

5, 11, 17, 23, 25, 29, 41, 43, 46, 47, 50, 53, 58, 59, 67, 71, 73, 77, 83, 85, 86, 89, 92, 94, 95, 101, 103, 107, 109, 113, 116, 118, 125, 131, 134, 137, 145, 146, 149, 151, 163, 167, 170, 172, 173, 178, 179, 181, 185, 188, 191, 193, 197, 202, 206, 209, 214, 215, 218, 219

Offset: 1

Jaroslav Krizek, Mar 07 2009

nonn

Numbers not occurring in A102187. The complement to A157846.

Zak Seidov, Table of n, a(n) for n = 1..1000

Cf. A102187, A003601, A000203, A000005.

Edited and extended by R. J. Mathar, Mar 15 2009

A162538 The smallest number with an arithmetic mean of divisors equal to n; 0 if nonexistent.

Original entry on oeis.org

1, 3, 5, 7, 0, 11, 13, 21, 17, 19, 0, 23, 45, 39, 29, 31, 0, 46, 37, 57, 41, 43, 0, 47, 0, 99, 53, 91, 0, 59, 61, 93, 86, 67, 116, 71, 73, 111, 125, 79, 0, 83, 0, 129, 89, 0, 0, 141, 97, 0, 101, 103, 0, 107, 109, 188, 113, 0, 0, 158, 169, 183, 166, 127, 261, 131, 0, 201, 137

Offset: 1

Claudio Meller, Jul 05 2009

nonn

a(n) is the smallest k such that sigma(k)/tau(k) = A000203(k)/A000005(k) = n.

Zeros occur if n is in A157847 (i.e., not in A157846).

			a(7)= 13 because sigma(13)=14 and tau(13)= 2 so 14/2 = 7.
a(8)= 21 because sigma(21)=32 and tau(21)= 4 so 32/4 = 8.

Cf. A003601.

Table[SelectFirst[Range[10^3],n*DivisorSigma[0,#]==DivisorSigma[1,#]&],{n,70}]/.(Missing["NotFound"]->0) (* Harvey P. Dale, Dec 14 2015 *)

Edited by R. J. Mathar, Aug 07 2009

cp's OEIS Frontend

A157847 Numbers which are not a mean of divisors of some arithmetic number A003601(k).

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