A075492 Numbers k such that sum of digits of k < number of divisors of k.

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

Comments

Solutions to A007953(x) < A000005(x).

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

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 *)

Prog

(PARI) isok(k) = sumdigits(k) < numdiv(k); \\ Amiram Eldar, Mar 05 2026

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