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

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A275998 Numbers n such that phi(n^2-1) = phi(n^2+1). 0
3, 27, 267, 8820000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No other terms below 10^8. - Michel Marcus, Aug 17 2016

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

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

MATHEMATICA

Select[Range@10000000, EulerPhi@(#^2 - 1) ==  EulerPhi[#^2 + 1] &] (* Vincenzo Librandi, Aug 18 2016 *)

PROG

(PARI) isok(n) = eulerphi(n^2-1) == eulerphi(n^2+1); \\ Michel Marcus, Aug 16 2016

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

CROSSREFS

Cf. A000010, A066812.

Sequence in context: A279658 A026294 A199688 * A098401 A011544 A127503

Adjacent sequences:  A275995 A275996 A275997 * A275999 A276000 A276001

KEYWORD

nonn,more

AUTHOR

Altug Alkan, Aug 16 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 17 12:18 EST 2020. Contains 330958 sequences. (Running on oeis4.)