A176238 Natural numbers n such that d(d(n)+1) > 2.

4, 9, 16, 24, 25, 30, 36, 40, 42, 49, 54, 56, 64, 66, 70, 78, 81, 88, 100, 102, 104, 105, 110, 114, 121, 128, 130, 135, 136, 138, 144, 152, 154, 165, 169, 170, 174, 182, 184, 186, 189, 190, 192, 195, 196, 222, 225, 230, 231, 232, 238, 240, 246, 248, 250, 255

Offset: 1

Author

Giovanni Teofilatto, Apr 12 2010

Keywords

• nonn

Comments

Complement to A166546.

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000005, A166546.

Programs

Mathematica

Select[Range[300],DivisorSigma[0,DivisorSigma[0,#]+1]>2&] (* Harvey P. Dale, Jul 15 2021 *)

Extensions

Extended by Giovanni Teofilatto, Apr 14 2010

Corrected (192 and 240 inserted) by R. J. Mathar, Apr 22 2010