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A162902 An increasing sequence of alternatingly squarefree and not squarefree numbers. 0
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 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..67.

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

Sequence in context: A141220 A092022 A190200 * A026491 A214026 A174396

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

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Last modified April 17 09:16 EDT 2014. Contains 240634 sequences.