A065552 a(n) = floor(sqrt(phi(10^n)*sigma(10^n) + 10^(3*n))).

1, 32, 1004, 31637, 1000048, 31622932, 1000000496, 31622778176, 1000000004990, 31622776617479, 1000000000049975, 31622776601841868, 1000000000000499938, 31622776601685374362, 1000000000000004999847, 31622776601683809131135, 1000000000000000049999618, 31622776601683793478102215

Offset

0,2

Comments

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

Links

Table of n, a(n) for n=0..17.

Mathematica

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

Crossrefs

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

Sequence in context: A170713 A170751 A218734 * A298193 A299087 A299343

Adjacent sequences: A065549 A065550 A065551 * A065553 A065554 A065555

Keyword

nonn

Author

Labos Elemer, Nov 13 2001

Extensions

a(0) = 1 prepended by, a(11)-a(15) corrected by, and a(16)-a(17) from Stefano Spezia, Mar 23 2023

Status

approved