OFFSET
0,6
COMMENTS
Provides interesting decomposition: phi(n) = u+w, where u and w consecutive terms of this sequence. Depends also on initial value.
LINKS
Amiram Eldar, Table of n, a(n) for n = 0..10000
FORMULA
a(n) + a(n-1) = A000010(n).
a(n) = (-1)^n * (1 - A068773(n)) for n >= 1. - Amiram Eldar, Mar 05 2024
MAPLE
A083239 := proc(n)
option remember ;
if n = 0 then
1 ;
else
numtheory[phi](n)-procname(n-1) ;
end if;
end proc:
seq(A083239(n), n=0..100) ; # R. J. Mathar, Jun 20 2021
MATHEMATICA
a[n_] := a[n] = EulerPhi[n] -a[n-1]; a[0] = 1; Table[a[n], {n, 0, 100}]
PROG
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Labos Elemer, Apr 23 2003
EXTENSIONS
a(0)=1 prepended by R. J. Mathar, Jun 20 2021
STATUS
approved