A336357 Numbers k such that sigma(k) has fewer distinct prime factors than k.

21, 30, 42, 66, 70, 84, 93, 102, 105, 110, 138, 154, 156, 165, 170, 186, 210, 217, 230, 231, 238, 255, 273, 282, 310, 318, 322, 330, 336, 345, 357, 364, 372, 374, 381, 385, 390, 399, 400, 420, 426, 434, 462, 465, 470, 483, 506, 510, 525, 530, 546, 561, 570, 595, 630, 642, 651, 658, 660, 682, 690, 705, 710, 714

Offset: 1

Author

Antti Karttunen, Jul 20 2020

Keywords

• nonn

Comments

Numbers k for which A058062(k) < A001221(k).

If terms x and y are present and gcd(x,y) = 1, then x*y is present also.

Crossrefs

Cf. A336355 (characteristic function), A336358 (complement).

Cf. also A055743, A336359.

Programs

Mathematica

Select[Range[800],PrimeNu[#]>PrimeNu[DivisorSigma[1,#]]&] (* Harvey P. Dale, Aug 07 2021 *)