login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A303809 Multiplicative with a(p^k) = 2^a(k). 3
1, 2, 2, 4, 2, 4, 2, 4, 4, 4, 2, 8, 2, 4, 4, 16, 2, 8, 2, 8, 4, 4, 2, 8, 4, 4, 4, 8, 2, 8, 2, 4, 4, 4, 4, 16, 2, 4, 4, 8, 2, 8, 2, 8, 8, 4, 2, 32, 4, 8, 4, 8, 2, 8, 4, 8, 4, 4, 2, 16, 2, 4, 8, 16, 4, 8, 2, 8, 4, 8, 2, 16, 2, 4, 8, 8, 4, 8, 2, 32, 16, 4, 2, 16 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence contains every power of 2; see A303819 for the corresponding least indices.

For any n > 0, a(n) only depends on the prime signature of n.

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000

FORMULA

a(n) <= n with equality iff n = A014221(k) for some k >= 0.

a(A002110(k)) = 2^k for any k >= 0.

a(n) = 2 iff n is prime.

PROG

(PARI) a(n) = my (f=factor(n)); prod (i=1, #f~, 2^a(f[i, 2]))

CROSSREFS

Cf. A002110, A014221, A061142, A303819.

Sequence in context: A040003 A106469 A082508 * A193562 A249868 A255311

Adjacent sequences:  A303806 A303807 A303808 * A303810 A303811 A303812

KEYWORD

nonn,easy,mult

AUTHOR

Rémy Sigrist, Apr 30 2018

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 February 16 14:47 EST 2019. Contains 320163 sequences. (Running on oeis4.)