OFFSET
1,1
COMMENTS
LINKS
Ray Chandler, Table of n, a(n) for n=1..1239
EXAMPLE
a(1)=9: A137576(4)=13 and 13-1 is divisible by phi(9)=6.
MATHEMATICA
A137576[n_] := Module[{t}, (t = MultiplicativeOrder[2, 2 n + 1])* DivisorSum[2 n + 1, EulerPhi[#]/MultiplicativeOrder[2, #] &] - t + 1];
okQ[n_] := OddQ[n] && CompositeQ[n] && Divisible[A137576[(n - 1)/2] - 1, EulerPhi[n]];
Reap[For[k = 1, k < 500, k += 2, If[okQ[k], Print[k]; Sow[k]]]][[2, 1]] (* Jean-François Alcover, Jan 11 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, May 04 2008
EXTENSIONS
Extended by Ray Chandler, May 08 2008
STATUS
approved