A271042 a(n) = k is the least squarefree number with a run of n >= 0 nonsquarefree numbers immediately preceding k and a run of zero nonsquarefree numbers immediately succeeding k.

2, 1, 10, 101, 246, 1685, 22026, 217077, 7216626, 8870033, 262315477, 221167433, 105779897634, 82462576233

Offset

0,1

Comments

This is the leftmost column (indexed by zero) of the doubly infinite matrix T(i,j) defined in A270996: a(n) = A270996(n*(n+1)/2).

Links

Table of n, a(n) for n=0..13.

Example

a(3) = 101 since 97, 101 and 102 are squarefree while 98, 99 and 100 constitute the first nonsquarefree triple followed by a pair of squarefree numbers.

Mathematica

(* We use function a270996[] from A270996 *)
Map[a270996[{0, 1000000}, {#, 0}]&, Range[0, 7]]
(* computes a(0)...a(7) *)

Crossrefs

Cf. A005117, A268330, A270344, A270996.

Sequence in context: A213421 A370068 A239070 * A098290 A160110 A258055

Adjacent sequences: A271039 A271040 A271041 * A271043 A271044 A271045

Keyword

nonn,more

Author

Hartmut F. W. Hoft, Mar 29 2016

Extensions

a(12)-a(13) from Kevin P. Thompson, Apr 19 2022

Status

approved