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

Author

Labos Elemer, Jul 15 2004

Keywords

• base
• nonn

Examples

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

Links

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

Crossrefs

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

Programs

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 *)