A284755 Numbers n such that the average of all proper divisors of all positive integers <= n is an integer.

2, 3, 63, 1249, 4696, 1200509

Offset: 1

Author

Ilya Gutkovskiy, Apr 02 2017

Keywords

• nonn
• more

Comments

Numbers n such that A002541(n)|A153485(n).

a(7) > 10^12. - Giovanni Resta, Apr 13 2017

Links

• Eric Weisstein's World of Mathematics, Restricted Divisor Function
• Index entries for sequences related to sums of divisors

Crossrefs

Cf. A000005, A000203, A001065, A002541, A003601, A023884, A023886, A027751, A153485, A226647, A284288.

Programs

Mathematica

Select[Range[2, 1300000], Mod[Sum[DivisorSigma[1, k] - k, {k, 1, #}], Sum[DivisorSigma[0, k] - 1, {k, 1, #}]] == 0 &]