OFFSET
1,4
COMMENTS
EXAMPLE
a(12)=4 because
f(12) = 12 - tau(phi(12)) = 12 - tau(4) = 12 - 3 = 9;
f(9) = 9 - tau(phi(9)) = 9 - tau(6) = 9 - 4 = 5;
f(5) = 5 - tau(phi(5)) = 5 - tau(4) = 5 - 3 = 2;
f(2) = 2 - tau(phi(2)) = 2 - tau(1) = 2 - 1 = 1, and a(12) = 4.
MAPLE
A062821 := proc(n)
numtheory[tau](numtheory[phi](n)) ;
end proc:
A176839 := proc(n)
a := 0 ;
x := n ;
while x <> 1 do
x := x-A062821(x) ;
a := a+1 ;
end do:
a ;
end proc: # R. J. Mathar, Oct 11 2011
MATHEMATICA
f[n_] := If[n == 1, 1, n - DivisorSigma[0, EulerPhi[n]]];
a[n_] := Length[FixedPointList[f, n]] - 2;
Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Apr 09 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Apr 27 2010
STATUS
approved