OFFSET
1,6
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
a(1) = 0, and for n > 1, a(n) = totient(cototient(n)) = A000010(A051953(n)). - Antti Karttunen, Aug 07 2017
MAPLE
A051953 := proc(n)
n-numtheory[phi](n) ;
end proc:
A054571 := proc(n)
numtheory[phi](A051953(n)) ;
end proc: # R. J. Mathar, Oct 13 2011
MATHEMATICA
Array[EulerPhi[# - EulerPhi@ #] &, 81] (* Michael De Vlieger, Aug 07 2017 *)
PROG
(PARI) A054571(n) = if(1==n, 0, eulerphi(n - eulerphi(n))); \\ Antti Karttunen, Aug 07 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
J. Sandor (mstaicu(AT)dualnet.ro), Mar 09 2002
EXTENSIONS
Description clarified with a(1) = 0 explicitly set by convention. - Antti Karttunen, Aug 07 2017
STATUS
approved