login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A331050 Positive integers whose number of factorizations into factors > 1 (A001055) is odd. 9
1, 2, 3, 5, 7, 8, 11, 13, 16, 17, 19, 23, 24, 27, 29, 30, 31, 32, 36, 37, 40, 41, 42, 43, 47, 53, 54, 56, 59, 60, 61, 64, 66, 67, 70, 71, 73, 78, 79, 81, 83, 84, 88, 89, 90, 96, 97, 100, 101, 102, 103, 104, 105, 107, 109, 110, 113, 114, 120, 125, 126, 127, 128 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

First differs from A319239 in lacking 256.

LINKS

Table of n, a(n) for n=1..63.

MATHEMATICA

facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];

Select[Range[100], OddQ[Length[facs[#]]]&]

CROSSREFS

Complement of A331051.

The version for powers of two (instead of odds) is A330977.

The version for primes (instead of odds) is A330991.

Cf. A001055, A001221, A001222, A002033, A005117, A045778, A045782, A045783, A330972, A330973.

Sequence in context: A287893 A051600 A319239 * A026410 A066720 A079851

Adjacent sequences:  A331047 A331048 A331049 * A331051 A331052 A331053

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 10 2020

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 7 12:19 EDT 2020. Contains 336276 sequences. (Running on oeis4.)