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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A015841 Numbers k such that phi(k) | sigma(k+4). 6

%I #22 Feb 12 2021 05:33:24

%S 1,2,3,6,7,8,10,17,18,24,26,42,50,52,54,56,65,75,80,81,87,90,110,111,

%T 114,120,126,154,164,186,216,234,244,245,306,308,338,344,350,351,371,

%U 372,374,416,436,456,490,528,560,570,598,626,682,689,759,777,836,866

%N Numbers k such that phi(k) | sigma(k+4).

%H Ivan Neretin, <a href="/A015841/b015841.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[3000],Divisible[DivisorSigma[1, 4 + #], EulerPhi[#]] &] (* _David Nacin_, Mar 03 2012 *)

%o (PARI) isok(n) = !(sigma(n+4) % eulerphi(n)); \\ _Michel Marcus_, Feb 05 2017

%K nonn

%O 1,2

%A _Robert G. Wilson v_

%E a(1) = 1 inserted by _Ivan Neretin_, Feb 05 2017

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 March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)