OFFSET
1,2
COMMENTS
Inspired by A134922.
MATHEMATICA
a[n_] =
If[EulerPhi[2*n - 1] - EulerPhi[2*n] == 0, n,
If[DivisorSigma[1, 2*n - 1] - DivisorSigma[1, 2*n] == 0, n,
If[Length[Divisors[2*n - 1]] - Length[Divisors[2*n]] == 0, n, {}]]];
Flatten[Table[a[n], {n, 1, 400}]]
CROSSREFS
KEYWORD
nonn,uned
AUTHOR
Roger L. Bagula, Oct 17 2008
STATUS
approved