A257550 Numbers n such that phi(n) = 5*phi(n+1).

17907119, 18828809, 31692569, 73421039, 179467469, 322757819, 337567229, 627702389, 975314339, 2537636009, 2722271369, 3328653509, 3917646809, 5529412349, 6369847469, 11179199849, 11201693579, 11363832479, 13442120999, 16781760449, 19751331599, 20002320029

Offset: 1

Author

Ray Chandler, Apr 29 2015

Keywords

• nonn

Examples

			phi(17907119) = 16588800 = 5*phi(17907120).
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..103 (terms < 10^12)

Crossrefs

Cf. A001274, A171262, A256907, A256937.

Programs

Mathematica

a1={};nmax=10^9;last=EulerPhi[1];n=2;
While[nRay Chandler, Apr 30 2015 *)

Extensions

a(10)-a(22) from Giovanni Resta, May 11 2015