A118728 - OEIS

A118728

a(n) = smallest squarefree number not less than a(n-1)+a(n-2), a(1)=1, a(0)=0.

0, 1, 2, 3, 5, 10, 15, 26, 41, 67, 109, 177, 286, 463, 749, 1213, 1963, 3178, 5141, 8319, 13461, 21781, 35242, 57023, 92265, 149289, 241554, 390845, 632399, 1023245, 1655645, 2678890, 4334537, 7013427, 11347966, 18361393, 29709359

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OFFSET

0,3

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

a(n) = A067535*(a(n-2)+a(n-1)) for n>1.

MATHEMATICA

Module[{lst={0, 1}}, Do[Module[{k=Total[Take[lst, -2]]}, While[!SquareFreeQ[ k], k++]; AppendTo[lst, k]], {40}]; Join[{0}, Drop[lst, 2]]] (* Harvey P. Dale, May 16 2012 *)

ssn[{a_, b_}]:=Module[{k=a+b}, While[!SquareFreeQ[k], k++]; k]; Join[{0}, Drop[NestList[ {#[[2]], ssn[#]}&, {0, 1}, 40][[;; , 1]], 2]] (* Harvey P. Dale, Aug 12 2024 *)

CROSSREFS

Cf. A000045, A005117.

Sequence in context: A004691 A133335 A062925 * A062860 A024369 A306006

Adjacent sequences: A118725 A118726 A118727 * A118729 A118730 A118731

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, May 21 2006

STATUS

approved