A333104 - OEIS

%I #7 Mar 07 2020 20:19:29

%S 10,22,98,118,230,266,1452,88894,114214,1274198,51675986,61177358,

%T 82986118

%N Unitary quasiperfect cototient numbers: numbers k such that the sum of the iterated unitary cototient function of k is equal to k+1.

%C a(14) > 10^9.

%e 10 is a term since A323410(10) = 6, A323410(6) = 4, A323410(4) = 1 and 6 + 4 + 1 = 11 = 10 + 1.

%t uphi[0] = 0; uphi[1] = 1; uphi[n_] := (Times @@ (Table[#[[1]]^#[[2]] - 1, {1}] & /@ FactorInteger[n]))[[1]]; ucot[n_] := n - uphi[n]; Select[Range[10^4], Plus @@ FixedPointList[ucot, #] == 2*# + 1 &]

%Y Cf. A082897, A286067, A323410, A330273, A333103.

%K nonn,more

%O 1,1

%A _Amiram Eldar_, Mar 07 2020