A107039 First differences of indices of squarefree Jacobsthal numbers.

1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 3, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1

Offset

1,8

Comments

First differences of A107037.

Links

Amiram Eldar, Table of n, a(n) for n = 1..898

Maple

A001045 := proc(n) option remember : if n <= 1 then n; else A001045(n-1)+2*A001045(n-2) ; fi ; end: A107037 := proc(nmax) local a, n; a := [] ; n := 1: while nops(a) < nmax do if numtheory[issqrfree]( A001045(n) ) then a := [op(a), n] ; fi ; n := n+1: od : RETURN(a) ; end: A107039 := proc(nmax) local a107037 ; a107037 := A107037(nmax+1) : [seq( a107037[i]-a107037[i-1], i=2..nmax)] ; end: op(A107039(120)) ; # R. J. Mathar, Aug 12 2007

Mathematica

Position[LinearRecurrence[{1, 2}, {0, 1}, 131], _?SquareFreeQ]-1 // Rest // Flatten // Differences (* Jean-François Alcover, Dec 09 2023 *)

Crossrefs

Cf. A001045, A005117, A107037.

Sequence in context: A124778 A037831 A188169 * A249771 A030615 A336766

Adjacent sequences: A107036 A107037 A107038 * A107040 A107041 A107042

Keyword

nonn

Author

Paul Barry, May 09 2005

Extensions

More terms from R. J. Mathar, Aug 12 2007

Offset corrected by Amiram Eldar, Feb 25 2024

Status

approved