A073248 Squarefree numbers k such that k+1 is also squarefree, but k-1 and k+2 are not.

10, 46, 61, 73, 82, 118, 122, 133, 145, 154, 173, 190, 205, 226, 246, 262, 273, 277, 290, 298, 313, 326, 334, 370, 373, 385, 406, 421, 426, 442, 457, 473, 478, 493, 505, 514, 526, 537, 565, 573, 586, 601, 606, 622, 626, 658, 673, 694, 709, 730, 733, 745

Offset: 1

Author

Reinhard Zumkeller, Jul 22 2002

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005117, A073250, A073247, A007675.

Programs

Maple

state:= [true,true,true,true]:
R:= NULL: count:= 0:
for n from 1 while count < 100 do
  state:= [state[2],state[3],state[4],numtheory:-issqrfree(n)];
  if state = [false,true,true,false] then
     R:= R, n-2; count:= count+1
  fi
od:
R; # Robert Israel, Mar 02 2022

Mathematica

Transpose[SequencePosition[Table[If[SquareFreeQ[n],1,0],{n,800}],{0,1,1,0}]][[1]]+1 (* The program uses the SequencePosition function from Mathematica version 10 *) (* Harvey P. Dale, Mar 09 2016 *)