A096841 Numbers n such that sum of divisors of these numbers gives a decimal repdigit.

1, 2, 3, 4, 5, 7, 43, 146, 365, 438, 443, 803, 887, 2221, 4442, 6663, 8887, 87876, 88183, 153837, 250244, 285597, 292860, 296294, 302877, 307674, 344268, 351612, 380718, 403398, 423260, 441821, 444443, 550238, 579038, 584438, 588974, 593163, 600363

Offset

1,2

Links

Giovanni Resta, Table of n, a(n) for n = 1..365

Example

n=43:sigma[43]=44; regular solutions:repdigit-1=prime.

Mathematica

rd[x_] := Length[Union[IntegerDigits[x]]] Do[s = rd[DivisorSigma[1, n]]; s1 = DivisorSigma[1, n]; If[Equal[s, 1], Print[{n, s1}]; ta[[u]] = n; u = u + 1], {n, 1, 1000000}]; ta; DivisorSigma[1, ta]
Select[Range[650000], Length[Union[IntegerDigits[DivisorSigma[1, #]]]]==1&] (* Harvey P. Dale, May 11 2019 *)

Crossrefs

Cf. A096503-A096508, A096841-A096846, A000203.

Sequence in context: A263043 A028980 A183108 * A029963 A259389 A277217

Adjacent sequences: A096838 A096839 A096840 * A096842 A096843 A096844

Keyword

base,nonn

Author

Labos Elemer, Jul 15 2004

Status

approved