A239274 Numbers k such that k' = sigma(k) - phi(k), where k' = A003415(k) is the arithmetic derivative of k.

1, 88, 1104, 492624, 30818736, 200827760, 1598249556, 4575586644, 8491046375, 8554970196, 29917317500, 54481242640, 202195886375, 3201891498000

Offset: 1

Author

Giovanni Resta, Mar 13 2014

Keywords

• nonn

Comments

a(15) > 10^13.

Crossrefs

Cf. A000010, A000203, A003415, A166374, A230164.

Programs

Mathematica

ad[1]=0; ad[n_]:=n*Total[(#1[[2]] / #1[[1]]&) /@ FactorInteger[n]]; Select[Range[500000], ad[#] == DivisorSigma[1,#] - EulerPhi[#] &]