A334118 Primitive terms of A334117: odd numbers m such that sigma(m, -1) >= 3/2 with no proper divisors sharing this property.

15, 21, 99, 117, 153, 171, 207, 429, 561, 627, 663, 741, 759, 783, 837, 957, 999, 1023, 1107, 1161, 1269, 1431, 1593, 1647, 1809, 1917, 1925, 1971, 2133, 2275, 2695, 2975, 3185, 4235, 5005, 6545, 6723, 7209, 7315, 7735, 7857, 8091, 8181, 8343, 8645, 8667, 8829, 8855

Offset

1,1

Comments

From Peter Munn, Jan 30 2026: (Start)

sigma(m, -1) can also be written sigma(m)/m = A000203(m)/m.

If we include 2 with the terms we get the equivalent set of primitives with the restriction to odd numbers removed.

(End)

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[1, 10^4, 2], DivisorSigma[-1, #] >= 3/2 && Max[DivisorSigma[-1, Most[Divisors[#]]]] < 3/2 &] (* Amiram Eldar, Dec 28 2024 *)

Prog

(PARI) list(lim)=my(v=List(), k); forfactored(n=15, lim\1, if(sigma(n, -1)>=3/2 && (k=n[1])%2, for(i=1, #v, if(k%v[i]==0, next(2))); listput(v, k))); Vec(v)

Crossrefs

Cf. A334117, A000203, A005231, A119240.

For related sets of primitives see A388019 (and its CROSSREFS).

Sequence in context: A190662 A274084 A350098 * A219918 A084931 A265153

Adjacent sequences: A334115 A334116 A334117 * A334119 A334120 A334121

Keyword

nonn

Author

Charles R Greathouse IV, Apr 14 2020

Status

approved