login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A275998 Numbers n such that phi(n^2-1) = phi(n^2+1). 0

%I

%S 3,27,267,8820000

%N Numbers n such that phi(n^2-1) = phi(n^2+1).

%C No other terms below 10^8. - _Michel Marcus_, Aug 17 2016

%e 3 is a term because phi(3^2-1) = phi(3^2+1).

%t Select[Range@10000000, EulerPhi@(#^2 - 1) == EulerPhi[#^2 + 1] &] (* _Vincenzo Librandi_, Aug 18 2016 *)

%o (PARI) isok(n) = eulerphi(n^2-1) == eulerphi(n^2+1); \\ _Michel Marcus_, Aug 16 2016

%o (MAGMA) [n: n in [2..100000] | EulerPhi(n^2-1) eq EulerPhi(n^2+1)]; // _Vincenzo Librandi_, Aug 18 2016

%Y Cf. A000010, A066812.

%K nonn,more

%O 1,1

%A _Altug Alkan_, Aug 16 2016

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 21 23:41 EST 2020. Contains 332113 sequences. (Running on oeis4.)