OFFSET
1,2
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..10000
Vaclav Kotesovec, Plot of a(n)/log(n)^2 for n = 1..10000
FORMULA
a(n) = Card(k: 1<=k<=n : k==0 (mod phi(k))) asymptotically: a(n) = C*log(n)^2 + o(log(n)^2) with C=0.6....
MATHEMATICA
Table[Length[Select[Range[n], Divisible[#, EulerPhi[#]] &]], {n, 1, 100}] (* Vaclav Kotesovec, Feb 16 2019 *)
Accumulate[Table[If[Divisible[n, EulerPhi[n]], 1, 0], {n, 80}]] (* Harvey P. Dale, Jul 04 2021 *)
PROG
(PARI) for(n=1, 150, print1(sum(i=1, n, if(i%eulerphi(i), 0, 1)), ", "))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 05 2002
STATUS
approved