A162902 An increasing sequence of alternatingly squarefree and nonsquarefree numbers.

1, 4, 5, 8, 10, 12, 13, 16, 17, 18, 19, 20, 21, 24, 26, 27, 29, 32, 33, 36, 37, 40, 41, 44, 46, 48, 51, 52, 53, 54, 55, 56, 57, 60, 61, 63, 65, 68, 69, 72, 73, 75, 77, 80, 82, 84, 85, 88, 89, 90, 91, 92, 93, 96, 97, 98, 101, 104, 105, 108, 109, 112, 113, 116, 118, 120, 122

Offset

1,2

Comments

Composed of elements of A005117 at odd indices and of A013929 at even indices such that first differences of the combined sequence remain positive and minimal.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

f[n_]:=Module[{a=m=0}, Do[If[FactorInteger[n][[m, 2]]>1, a=1], {m, Length[FactorInteger[n]]}]; a]; q=0; lst={}; Do[If[f[n]==q, If[q==1, q=0, q=1]; AppendTo[lst, n]], {n, 6!}]; lst

Crossrefs

Cf. A005117, A013929.

Sequence in context: A346302 A377897 A190200 * A026491 A347476 A255491

Adjacent sequences: A162899 A162900 A162901 * A162903 A162904 A162905

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Jul 16 2009

Extensions

Edited by R. J. Mathar, Jul 21 2009

Status

approved