OFFSET
1,2
LINKS
Paolo Xausa, Table of n, a(n) for n = 1..1000
FORMULA
For n >= 3, a(n) mod 4 = 0. - Paolo Xausa, Jul 25 2022
MATHEMATICA
A018804[n_]:=Apply[Times, Apply[((#1-1)#2/#1+1)#1^#2&, FactorInteger[n], {1}]]; (* After Amiram Eldar in A018804 *)
upto=10^5; Join[{1, 2}, Reap[Do[If[Divisible[A018804[k], EulerPhi[k]], Sow[k]], {k, 4, upto, 4}]][[-1, -1]]] (* Paolo Xausa, Jul 25 2022 *)
PROG
(PARI) isok(k) = !(sumdiv(k, d, k*eulerphi(d)/d) % eulerphi(k)); \\ Michel Marcus, Nov 27 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, Nov 27 2021
STATUS
approved