A279011 - OEIS

%I #19 Sep 08 2022 08:46:18

%S 1,2,12,152,222,268,362,432,723,992,1517,2532,2567,8472,9718,9858,

%T 13498,15738,34732,35898,44092,60363,69312,75168,75973,82752,87208,

%U 88888,98198,105852,114392,126848,128672,135368,141093,161268,221223,233788,301513,328358

%N Numbers k such that phi(6k) is either phi(6k-2) or phi(6k+2), where phi is Euler's totient function A000010.

%H Dov Jarden, <a href="/A001602/a001602.pdf">Recurring Sequences</a>, Riveon Lematematika, Jerusalem, 1966. [Annotated scanned copy] See p. 67.

%t Select[Range[10^6], Function[k, Or @@ Map[EulerPhi[6 k] == EulerPhi@ # &, 6 k + {-2, 2}]]] (* _Michael De Vlieger_, Dec 12 2016 *)

%o (Magma) [n: n in [1..1000000] | not (EulerPhi(6*n) eq EulerPhi(6*n-2)) eq (EulerPhi(6*n) eq EulerPhi(6*n+2))]; // _Vincenzo Librandi_, Dec 12 2016

%Y Cf. A000010.

%Y Union of A279183 and A279184.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, Dec 10 2016

%E More terms from _Vincenzo Librandi_, Dec 12 2016