A217141 Numbers n such that phi(n) = phi(n+12) and n is not divisible by 2.

143, 157, 203, 247, 273, 1147, 1209, 1679, 2147, 2279, 2375, 2445, 2705, 2747, 4331, 4687, 5049, 6107, 7367, 7835, 7869, 7979, 7991, 9167, 12127, 17145, 18501, 18753, 18981, 19803, 22987, 26733, 27359, 29097, 29987, 32829, 35485, 35763, 37653, 37851, 39907

Offset: 1

Author

Michel Marcus, Sep 27 2012

Keywords

• nonn
• changed

Links

• Donovan Johnson, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000010, A179188, A217139.

Programs

Mathematica

Select[Range[1,40000,2],EulerPhi[#]==EulerPhi[#+12]&] (* Harvey P. Dale, Aug 22 2025 *)

PARI

{op=vector(N=12); Nd6=N/6;for( n=1, 1e4, if( op[n%N+1]+0==op[n%N+1]=eulerphi(n), if ((n-N) % Nd6 != 0, print1(n-N, ", "))))}

Extensions

Definition clarified by Harvey P. Dale, Aug 22 2025