A068360 Numbers n such that there is no squarefree number between prime(n) and prime(n+1).

1, 2, 5, 7, 17, 20, 25, 28, 35, 41, 43, 45, 49, 52, 57, 64, 69, 70, 81, 83, 98, 109, 120, 140, 144, 152, 171, 173, 176, 178, 182, 190, 206, 215, 225, 229, 230, 236, 253, 256, 261, 262, 277, 286, 294, 296, 302, 307, 315, 318, 323, 336, 346, 348, 373, 377, 390

Offset: 1

Author

Benoit Cloitre, Feb 28 2002

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A061398.

Programs

Mathematica

Join[{1},PrimePi/@Transpose[With[{prs=Partition[Prime[Range[ 400]],2,1]}, Select[ prs,Union[SquareFreeQ/@Range[#[[1]]+1,#[[2]]-1]]=={False}&]]][[1]]] (* Harvey P. Dale, Jan 24 2013 *)

Formula

n such that A061398(n)=0