A166987 Members of A143610 for which both neighbors are squarefree.

72, 108, 200, 392, 500, 968, 1352, 1372, 4232, 7688, 8788, 13448, 14792, 17672, 19652, 27436, 27848, 35912, 48668, 49928, 55112, 75272, 81608, 84872, 97556, 102152, 119164, 137288, 150152, 154568, 177608, 182408, 197192, 202612, 223112

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Oct 26 2009

Keywords

• nonn

Comments

Numbers of the form n=p^2*q^3 where p and q are two different primes and where n+1 and n-1 are both in A005117.

Crossrefs

Cf. A067874.

Programs

Mathematica

f[n_]:=Last/@FactorInteger[n]=={2,3}||Last/@FactorInteger[n]=={3,2}; << NumberTheory`NumberTheoryFunctions` lst={};Do[If[f[n],If[SquareFreeQ[n-1]&&SquareFreeQ[n+1], AppendTo[lst,n]]],{n,3*9!}];lst

Extensions

Definition narrowed by R. J. Mathar, Oct 28 2009