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

1,1

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.

Links

Table of n, a(n) for n=1..64.

Mathematica

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

Crossrefs

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

Cf. also A055743, A336359.

Sequence in context: A225653 A363609 A379019 * A317772 A308339 A186455

Adjacent sequences: A336354 A336355 A336356 * A336358 A336359 A336360

Keyword

nonn

Author

Antti Karttunen, Jul 20 2020

Status

approved