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

 

Logo

The OEIS is looking to hire part-time people to help edit core sequences, upload scanned documents, process citations, fix broken links, etc. - Neil Sloane, njasloane@gmail.com

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A279509 a(n) = largest number k such that floor(phi(k)/tau(k)) = n. 2
12, 60, 180, 240, 420, 480, 840, 462, 1260, 1680, 1440, 690, 2520, 2100, 2160, 2310, 3360, 2400, 3780, 5040, 4620, 3600, 3300, 1410, 5460, 4080, 6300, 7560, 5880, 4140, 9240, 2646, 10080, 6600, 6480, 7200, 10920, 8820, 9360, 2370, 13860, 8640, 8160, 15120 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(n) = largest number k such that floor(A000010(k)/A000005(k)) = A279507(k) = n.

Sequences b_n of numbers k such that floor(phi(k)/tau(k)) = n for n = 0..2:

b_0: 2, 4, 6, 12;

b_1: 1, 3, 8, 10, 14, 16, 18, 20, 24, 30, 36, 42, 48, 60;

b_2: 5, 9, 15, 22, 28, 32, 40, 54, 66, 72, 84, 90, 96, 120, 180.

Sequences b_n are finite for all n >= 0. See A279508 (smallest number k such that floor(phi(k)/tau(k)) = n).

LINKS

Table of n, a(n) for n=0..43.

EXAMPLE

For n = 1; a(1) = 60 because 60 is the largest number with floor(phi(60)/tau(60)) = floor(16/12) = 1.

PROG

(MAGMA) [Max([n: n in[1..100000] | Floor(EulerPhi(n) / NumberOfDivisors(n)) eq k]): k in [0..50]]

CROSSREFS

Cf. A000005, A000010, A020488, A020490, A279289, A279507, A279508.

Sequence in context: A153792 A229616 A000141 * A008530 A112415 A033486

Adjacent sequences:  A279506 A279507 A279508 * A279510 A279511 A279512

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Dec 19 2016

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified May 26 18:26 EDT 2017. Contains 287129 sequences.