A325654 Numbers m with a divisor d satisfying sigma(d) = 2*m.

6, 28, 496, 8128, 60480, 65520, 4357080, 33550336, 47139840, 91065600, 285981696, 2758909440, 8589869056, 87722956800, 132867440640, 137438691328, 306007080960, 806062473216, 1409150457792, 363485766938112, 12177456042320640, 29884246553283840

Offset: 1

Author

Jaroslav Krizek, May 12 2019

Keywords

• nonn

Comments

Even perfect numbers from A000396 are terms.

Numbers of the form A007691(k)*A054030(k)/2 when A054030(k) is even.

Subsequence of A323652.

Numbers of the form sigma(A325637(k))/2. - Jinyuan Wang, Jun 09 2019

Examples

			60480 is a term because 30240 divides 60480 and sigma(30240) = 120960 = 2*60480.
		

Links

• Vaclav Kotesovec, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000203, A000396, A007691, A054030, A323652, A325637.

Programs

Magma

[n: n in [1..100000] | #[d: d in Divisors(n) | SumOfDivisors(d) eq 2*n] gt 0];

PARI

isok(n) = fordiv(n, d, if (sigma(d) == 2*n, return(1))); 0; \\ Michel Marcus, May 12 2019

Extensions

More terms from Jinyuan Wang, Jun 09 2019