OFFSET
1,1
EXAMPLE
a(1)=2 and U(2)=1=U(3) so 3 is not in the sequence. U(4)=1/2 so a(2)=4.
MATHEMATICA
u = <|1 -> 1|>; L = {2}; Do[v = EulerPhi[n]/(2 Floor[n/2]); If[! KeyExistsQ[u, v], AppendTo[L, n]; u[v] = 1], {n, 3, 140}]; L (* Giovanni Resta, Jan 06 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Nick Bryant, Jan 05 2020
STATUS
approved