A063739 Squarefree numbers k such that phi(k) = phi(k+1).

1, 3, 15, 194, 255, 2834, 3255, 3705, 5186, 5187, 11715, 22935, 25545, 49215, 49335, 65535, 214334, 256274, 388245, 525986, 568815, 589407, 840255, 936494, 1259642, 1574727, 1659585, 1759874, 1788254, 2123583, 2200694, 2521694, 2619705, 3240614, 3289934

Offset: 1

Author

Jason Earls, Aug 13 2001

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..3547 (terms below 10^13 calculated from the b-file at A001274; terms 1..75 from Harry J. Smith, terms 76..1000 from Donovan Johnson)

Crossrefs

Intersection of A005117 and A001274.

Programs

Mathematica

Select[Range[3000000],SquareFreeQ[#]&&EulerPhi[#]==EulerPhi[#+1]&] (* Harvey P. Dale, May 15 2013 *)

PARI

for(n=1,10^7, if(issquarefree(n), if(eulerphi(n)==eulerphi(n+1),print(n))))

PARI

{ n=0; for (m=1, 10^9, if (eulerphi(m)==eulerphi(m + 1) && issquarefree(m), write("b063739.txt", n++, " ", m); if (n==75, break)) ) } \\ Harry J. Smith, Aug 29 2009