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

1,1

Comments

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

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

Links

Table of n, a(n) for n=1..6.

Eric Weisstein's World of Mathematics, Restricted Divisor Function

Index entries for sequences related to sums of divisors

Mathematica

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

Crossrefs

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

Sequence in context: A093551 A173915 A293041 * A061452 A369903 A280582

Adjacent sequences: A284752 A284753 A284754 * A284756 A284757 A284758

Keyword

nonn,more

Author

Ilya Gutkovskiy, Apr 02 2017

Status

approved