A117483 Numbers k for which pi(phi(k)) equals phi(pi(k)).

0, 1, 3, 4, 5, 8, 10, 11, 17, 20, 22, 30, 31, 41, 50, 59, 67, 75, 83, 109, 127, 157, 174, 179, 191, 200, 211, 241, 277, 283, 331, 353, 360, 367, 401, 414, 431, 460, 461, 475, 509, 547, 563, 587, 599, 617, 709, 739, 773, 797, 859, 877, 919, 942, 960, 967, 991, 1014

Offset

1,3

Links

Table of n, a(n) for n=1..58.

Example

75 is a term because pi(phi(75)) = pi(40) = 12 and phi(pi(75)) = phi(21) = 12;
0 is a term since pi(phi(0)) = pi(0) = 0 and phi(pi(0)) = phi(0) = 0;
1 is a term since pi(phi(1)) = pi(1) = 0 and phi(pi(1)) = phi(0) = 0.

Maple

with(numtheory): a:=proc(n) if pi(phi(n))=phi(pi(n)) then n else fi end: seq(a(n), n=0..1350); # Emeric Deutsch, Apr 30 2006

Mathematica

Select[Range[0, 1030], PrimePi@ EulerPhi@# == EulerPhi@ PrimePi@# &] (* Robert G. Wilson v *)

Crossrefs

Sequence in context: A184776 A202104 A190246 * A213513 A344168 A239142

Adjacent sequences: A117480 A117481 A117482 * A117484 A117485 A117486

Keyword

nonn

Author

Luc Stevens (lms022(AT)yahoo.com), Apr 25 2006

Extensions

More terms from Robert G. Wilson v and Emeric Deutsch, Apr 27 2006

Edited by Jon E. Schoenfield, Feb 06 2019

Status

approved