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

1,1

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.

Links

Table of n, a(n) for n=1..35.

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

Crossrefs

Cf. A067874.

Sequence in context: A052486 A114128 A143610 * A339940 A251124 A169644

Adjacent sequences: A166984 A166985 A166986 * A166988 A166989 A166990

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Oct 26 2009

Extensions

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

Status

approved