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 A209628 Number of squarefree numbers < n that are not prime. 0
 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 5, 5, 5, 5, 5, 5, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 10, 11, 12, 12, 12, 13, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 19, 20, 20, 20, 20, 21, 21, 21, 22, 23, 23, 23, 24, 25, 25, 25, 25, 26 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 LINKS Table of n, a(n) for n=1..74. FORMULA a(n) = A013928(n+1) - A000720(n). [Corrected by Georg Fischer, Dec 13 2022] MATHEMATICA Accumulate[Table[Boole[SquareFreeQ[n]&&!PrimeQ[n]], {n, 1, 100}]] CROSSREFS Cf. A000720, A013928, A005117, A000040. Sequence in context: A194621 A088004 A070548 * A132011 A363822 A054893 Adjacent sequences: A209625 A209626 A209627 * A209629 A209630 A209631 KEYWORD nonn AUTHOR Enrique Pérez Herrero, Mar 13 2012 STATUS approved

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Last modified August 6 15:42 EDT 2024. Contains 374974 sequences. (Running on oeis4.)