OFFSET
1,4
COMMENTS
a(2n) is a nonpositive even number while a(2n-1) is an odd positive number.
Abs(a(n)) < abs(a(n+1)) for 1 < n < 8000.
FORMULA
a(n) = Sum_{k=1..n} (-1)^(n-k)*binomial(n-1,k-1)*phi(k). - Ridouane Oudra, Aug 21 2021
a(n) = Sum_{k=1..n} (-1)^(n-k)*binomial(n,k)*A002088(k). - Ridouane Oudra, Oct 02 2022
EXAMPLE
MATHEMATICA
f[n_] := Differences[ Array[ EulerPhi, n], n -1][[1]]; Array[f, 34] (* or *)
nmx = 34; Join[ {1}, Differences[ Array[ EulerPhi, nmx], #][[1]] & /@ Range[nmx - 1]]
CROSSREFS
KEYWORD
sign
AUTHOR
Robert G. Wilson v, Jan 20 2020
STATUS
approved