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

3, 27, 267, 8820000

Offset: 1

Author

Altug Alkan, Aug 16 2016

Keywords

• nonn
• more

Comments

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

Examples

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

Crossrefs

Cf. A000010, A066812.

Programs

Magma

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

Mathematica

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

PARI

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