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

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A074891 Numbers n such that sigma(n) = phi(3n). 3
15, 35, 357, 1045, 3339, 5049, 10659, 12441, 24871, 24969, 29029, 50065, 58435, 64285, 87685, 99693, 132957, 137885, 140335, 353133, 423657, 596037, 655707, 734517, 745503, 894387, 1390753, 1406427, 1529983, 1641783, 1739507, 1823877 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..500

EXAMPLE

sigma(15) = 24 = phi(3 * 15), so 15 is a term of the sequence.

MATHEMATICA

Select[ Range[1936556], EulerPhi[3# ] == DivisorSigma[1, # ] &]

PROG

(PARI) is(n)=sigma(n)==eulerphi(3*n) \\ Charles R Greathouse IV, Dec 09 2013

CROSSREFS

Sequence in context: A027442 A208728 A219689 * A271733 A241282 A249056

Adjacent sequences:  A074888 A074889 A074890 * A074892 A074893 A074894

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Sep 13 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Sep 17 2002

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 December 7 23:08 EST 2016. Contains 278900 sequences.