A065552 - OEIS

%I #13 Mar 23 2023 17:34:05

%S 1,32,1004,31637,1000048,31622932,1000000496,31622778176,

%T 1000000004990,31622776617479,1000000000049975,31622776601841868,

%U 1000000000000499938,31622776601685374362,1000000000000004999847,31622776601683809131135,1000000000000000049999618,31622776601683793478102215

%N a(n) = floor(sqrt(phi(10^n)*sigma(10^n) + 10^(3*n))).

%C Similar results are obtained if the cube is replaced with other odd powers.

%t a[n_]:=Floor[Sqrt[EulerPhi[10^n]DivisorSigma[1,10^n]+10^(3n)]]; Array[a,17,0] (* _Stefano Spezia_, Mar 23 2023 *)

%Y Cf. A000010, A000203, A062354, A065655, A065656.

%K nonn

%O 0,2

%A _Labos Elemer_, Nov 13 2001

%E a(0) = 1 prepended by, a(11)-a(15) corrected by, and a(16)-a(17) from _Stefano Spezia_, Mar 23 2023