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Search: id:A130025
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| A130025 |
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a(1)=1. a(n) = a(n-1) + (number of terms, from among terms a(1) through a(n-1), which are squarefree). |
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+0
1
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| 1, 2, 4, 6, 9, 12, 15, 19, 24, 29, 35, 42, 50, 58, 67, 77, 88, 99, 110, 122, 135, 148, 161, 175, 189, 203, 218, 234, 250, 266, 283, 301, 320, 339, 359, 380, 401, 423, 445, 468, 491, 515, 540, 565, 591, 618, 646, 675, 704, 733, 763, 794, 826, 859, 893, 928, 963
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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Among the first 8 terms of the sequence there are 5 squarefree integers (1,2,6,15,19). So a(9) = a(8) + 5 = 24.
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MAPLE
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with(numtheory): a[1] := 1: for n from 2 to 60 do ct := 0: for j to n-1 do if abs(mobius(a[j])) > 0 then ct := ct+1 else ct := ct end if end do: a[n] := a[n-1]+ct end do: seq(a[n], n = 1 .. 60); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jul 18 2007
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CROSSREFS
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Adjacent sequences: A130022 A130023 A130024 this_sequence A130026 A130027 A130028
Sequence in context: A118103 A003066 A075349 this_sequence A076271 A036441 A134678
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Jun 20 2007
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu) and Joshua Zucker (joshua.zucker(AT)stanfordalumni.org), Jul 18 2007
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