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
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 1..898
Programs
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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
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Mathematica
Position[LinearRecurrence[{1, 2}, {0, 1}, 131], ?SquareFreeQ]-1 // Rest // Flatten // Differences (* _Jean-François Alcover, Dec 09 2023 *)
Extensions
More terms from R. J. Mathar, Aug 12 2007
Offset corrected by Amiram Eldar, Feb 25 2024
Comments