A013931 a(n) is squarefree and sum of all squarefrees <= a(n) is squarefree.

1, 2, 3, 5, 6, 10, 13, 15, 19, 22, 26, 30, 31, 35, 38, 39, 41, 43, 51, 55, 59, 65, 66, 67, 69, 70, 73, 74, 78, 79, 82, 85, 86, 89, 93, 95, 97, 102, 103, 105, 110, 111, 113, 118, 122, 123, 129, 130, 131, 133, 134, 137, 139, 142, 143, 145, 149, 154, 155, 157, 159, 163, 166, 167

Offset: 1

Author

Henri Lifchitz

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harvey P. Dale)

Crossrefs

Cf. A005117, A013930, A013932.

Programs

Mathematica

Module[{nn=200,sf},sf=Select[Range[nn],SquareFreeQ];Transpose[ Select[ Thread[ {sf, Accumulate[sf]}],SquareFreeQ[Last[#]]&]][[1]]] (* Harvey P. Dale, Feb 09 2013 *)

Formula

a(n) = A005117(A013930(n)). - Amiram Eldar, Mar 07 2021

Extensions

More terms from David W. Wilson