login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A086420 Euler's totient of 3-smooth numbers: a(n) = A000010(A003586(n)). 1
1, 1, 2, 2, 2, 4, 6, 4, 8, 6, 8, 18, 16, 12, 16, 18, 32, 24, 54, 32, 36, 64, 48, 54, 64, 72, 162, 128, 96, 108, 128, 144, 162, 256, 192, 216, 486, 256, 288, 324, 512, 384, 432, 486, 512, 576, 648, 1024, 1458, 768, 864, 972, 1024, 1152, 1296, 2048, 1458, 1536 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) is 3-smooth.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Totient Function.

Eric Weisstein's World of Mathematics, Smooth Number.

FORMULA

n>1: a(n) = A003586(n) * (if A003586(n) mod 3 > 0 then 1/2 else (1 + A003586(n) mod 2)/3), a(1) = 1.

Sum_{n>=1} 1/a(n) = 21/4. - Amiram Eldar, Dec 21 2020

MATHEMATICA

s = {}; m = 12; Do[n = 3^k; While[n <= 3^m, AppendTo[s, n]; n*=2], {k, 0, m}]; EulerPhi /@ Union[s] (* Amiram Eldar, Jan 29 2020 *)

CROSSREFS

Cf. A000010, A003586.

Sequence in context: A217637 A231515 A231544 * A328106 A342336 A320908

Adjacent sequences: A086417 A086418 A086419 * A086421 A086422 A086423

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 18 2003

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 11:56 EST 2022. Contains 358586 sequences. (Running on oeis4.)