A157848 Corresponding values of arithmetic means of divisors of numbers from A007340.

1, 3, 28, 45, 84, 182, 270, 620, 546, 1240, 1330, 1638, 1260, 1365, 2660, 8128, 6200, 6200, 6944, 8190, 9310, 7560, 8190, 18600, 15120, 18620, 16380, 25935, 30240, 32760, 63700, 55860, 40950, 55800, 117800, 98208, 105664, 117800, 121030, 173600, 167400, 155610

Offset: 1

Author

Jaroslav Krizek, Mar 07 2009, Mar 09 2009

Keywords

• nonn

Comments

A007340 = numbers k such that the arithmetic mean of divisors of k is an integer and equal to one of the divisors of this numbers.

Examples

			a(3) = 28, because 28 is arithmetic mean of divisors of A007340(3)=140 and also is divisor of 140.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..847 (calculated from the b-file at A007340)

Crossrefs

Cf. A000203, A007340, A000005.

Programs

PARI

lista(kmax) = {my(f, s, d); for(k = 1, kmax, f = factor(k); s = sigma(f); d = numdiv(f); if(!(s % d) && denominator(d / sigma(f, -1)) == 1, print1(s/d, ", ")));} \\ Amiram Eldar, Apr 15 2024

Formula

a(n) = sigma(A007340(n))/tau(A007340(n)) = A000203(A007340(n))/A000005(A007340(n)).

Extensions

Corrected and extended by Jaroslav Krizek, Mar 29 2015