A245775 Numbers k such that A017666(k) = denominator(sigma(k)/k) = 3.

3, 12, 84, 234, 270, 1080, 1488, 1638, 6048, 6552, 24384, 35640, 199584, 435708, 2142720, 4713984, 12999168, 18506880, 36197280, 100651008, 208565280, 240589440, 275890944, 299980800, 470564640, 3899750400, 4138364160, 6039429120, 13286744064, 17827568640

Offset: 1

Author

Jaroslav Krizek, Aug 26 2014

Keywords

• nonn

Comments

Numbers n such that sigma(n)/n = k + 1/3 with integer k are terms of this sequence (3, 12, 234, 1080, 6048, 6552, 435708, 4713984, ...).

Subsequence of A245774 (numbers n such that n divides 3*sigma(n)).

Union of A160320 (sigma(n)/n = k + 1/3) and A160321 (sigma(n)/n = k + 2/3). - Michel Marcus, Aug 27 2014

Examples

			Number 12 is in sequence because A017666(12) = 3.
		

Links

• Jud McCranie, Table of n, a(n) for n = 1..44 (terms <= 10^13).

Crossrefs

Cf. A000203, A007691, A160320, A160321, A245774.

Programs

Magma

[n: n in [1..3000000] | Denominator((SumOfDivisors(n))/n) eq 3]

PARI

for(n=1,10^7,if(denominator(sigma(n)/n)==3,print1(n,", "))) \\ Derek Orr, Aug 26 2014

Extensions

More terms from A160320 and A160321 by Michel Marcus, Aug 27 2014