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A026422 a(n) = least positive integer > a(n-1) and not a(i)*a(j) for 1 <= i <= j < n. 3
1, 2, 3, 5, 7, 8, 11, 12, 13, 17, 18, 19, 20, 23, 27, 28, 29, 30, 31, 32, 37, 41, 42, 43, 44, 45, 47, 48, 50, 52, 53, 59, 61, 63, 66, 67, 68, 70, 71, 72, 73, 75, 76, 78, 79, 80, 83, 89, 92, 97, 98, 99, 101, 102, 103, 105, 107, 108, 109, 110 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..5000

MATHEMATICA

a[1]=1; a[n_] := a[n] = (t= Union[Flatten[Table[a[i] a[j], {i, 1, n-1}, {j, i, n-1}]]]; Do[If[FreeQ[t, k], an = k; Break[]], {k, a[n-1]+1, Last[t]+1}]; an); Array[a, 60] (* Jean-Fran├žois Alcover, May 06 2011 *)

Select[Range[110], OddQ[Total[FactorInteger[#]][[2]]] &] (* T. D. Noe, May 07 2011 *)

PROG

(PARI) is(n)=bigomega(n)%2 || n==1 \\ Charles R Greathouse IV, Sep 16 2015

CROSSREFS

Apart from initial term, same as A026424.

Cf. A026416 and references therein.

Sequence in context: A100959 A245303 A166982 * A026424 A298207 A229125

Adjacent sequences:  A026419 A026420 A026421 * A026423 A026424 A026425

KEYWORD

nonn

AUTHOR

Clark Kimberling

EXTENSIONS

Name corrected by Charles R Greathouse IV, Sep 16 2015

STATUS

approved

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Last modified November 12 09:29 EST 2019. Contains 329054 sequences. (Running on oeis4.)