A275998 Numbers n such that phi(n^2-1) = phi(n^2+1).

3, 27, 267, 8820000

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: A378612 A026294 A199688 * A098401 A355363 A011544

Adjacent sequences: A275995 A275996 A275997 * A275999 A276000 A276001

Keyword

nonn,more

Author

Altug Alkan, Aug 16 2016

Status

approved