A067926 a(n)=phi(n^2+1)/n if (n^2+1) is composite and phi(n^2+1)==0 (mod n).

6, 25, 48, 60, 98, 150, 192, 304, 336, 896, 990, 800, 1248, 1232, 1210, 1105, 1798, 2448, 2790, 4032, 5166, 5095, 7488, 8925, 9798, 8484, 12540, 12528, 14448, 14112, 15994, 12950, 19998, 21312, 21222, 24198, 12288, 35768, 26560, 33792, 46620

Offset

1,1

Comments

If n^2+1 is prime, trivially phi(n^2+1)/n=n.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..100

Mathematica

cep[n_]:=Module[{c=n^2+1, ep}, ep=EulerPhi[c]; If[CompositeQ[c] && Mod[ ep, n] == 0, ep/n, Nothing]]; Array[cep, 47000] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 25 2021 *)

Crossrefs

Cf. A066820.

Sequence in context: A079606 A372750 A184852 * A165217 A320422 A075224

Adjacent sequences: A067923 A067924 A067925 * A067927 A067928 A067929

Keyword

easy,nonn

Author

Benoit Cloitre, Feb 22 2002

Status

approved