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!)
A193509 Number of odd divisors of Omega(n). 4
0, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 2, 2, 1, 2, 1, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,8

COMMENTS

Omega(n) is the number of prime divisors of n counted with multiplicity, A001222 (also called bigomega(n)).

Records are at 2^A053624(n). [Charles R Greathouse IV, Jul 29 2011]

LINKS

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

EXAMPLE

a(8) = 2 because Omega(8) = 3 and the 2 odd divisors are {1, 3}.

MATHEMATICA

f[n_] := Block[{d = Divisors[PrimeOmega[n]]}, Count[OddQ[d], True]]; Table[f[n], {n, 80}]

PROG

(PARI) a(n)=if(n==1, 0, my(k=bigomega(n)); numdiv(k>>valuation(k, 2))) \\ Charles R Greathouse IV, Jul 29 2011

CROSSREFS

Cf. A001222.

Sequence in context: A338274 A210960 A339095 * A331284 A331591 A003649

Adjacent sequences:  A193506 A193507 A193508 * A193510 A193511 A193512

KEYWORD

nonn

AUTHOR

Michel Lagneau, Jul 29 2011

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 April 11 12:38 EDT 2021. Contains 342886 sequences. (Running on oeis4.)