A140198 A002326((k-1)/2) for composite numbers k from A141229.

18, 100, 1210, 2028, 6498, 23548, 49284, 146068, 201898, 223260, 296274, 564898, 1020100, 1213594, 2230930, 2666298, 3285748, 4304178, 5147788, 5703298, 5896980, 7606564, 9349410, 11645554, 19392748, 25067908, 31754524, 41661514, 42386748, 51755988, 54296298

Offset: 1

Author

Vladimir Shevelev, Jun 15 2008

Keywords

• nonn

Crossrefs

Cf. A002326, A141229, A001122, A006694.

Programs

Mathematica

r[n_] := EulerPhi[n]/MultiplicativeOrder[2, n]; d[n_] := DivisorSum[n, r[#] &]; f[n_] := (m = MultiplicativeOrder[2, n])*d[n] - m + 1; MultiplicativeOrder[2, #] & /@  Select[Range[10^5], CompositeQ[#] && Total@(r /@ Divisors[#]) - 1 == 3 &] (* Amiram Eldar, Sep 12 2019 *)

Extensions

a(4) corrected and more terms added by Amiram Eldar, Sep 12 2019