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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
OFFSET
1,6
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
KEYWORD
nonn
AUTHOR
STATUS
approved