A075492 Sum of digits of n < number of divisors of n.

10, 12, 20, 21, 24, 30, 32, 40, 42, 50, 60, 70, 72, 80, 90, 100, 102, 104, 105, 108, 110, 111, 112, 114, 120, 126, 130, 132, 140, 144, 150, 160, 162, 168, 180, 192, 200, 201, 204, 210, 212, 216, 220, 222, 224, 230, 231, 232, 234, 240, 250, 252, 260, 264, 270

Offset

1,1

Links

Table of n, a(n) for n=1..55.

Formula

Solutions to A007953[x] < A000005[x]

Example

All are special composites.

Mathematica

sud[x_] := Apply[Plus, IntegerDigits[x]] Do[s=sud[n]-DivisorSigma[0, n]; If[s>0, Print[n]], {n, 1, 256}]
Select[Range[300], Total[IntegerDigits[#]]<DivisorSigma[0, #]&] (* Harvey P. Dale, Apr 05 2015 *)

Crossrefs

Cf. A007953, A000005, A057531, A075492, A075493.

Sequence in context: A048378 A338640 A129845 * A225742 A338855 A221638

Adjacent sequences: A075489 A075490 A075491 * A075493 A075494 A075495

Keyword

base,easy,nonn

Author

Labos Elemer, Sep 26 2002

Status

approved