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A160813
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a(n) = n-th squarefree number plus n-th cube-free number.
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0
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2, 4, 6, 9, 11, 13, 17, 20, 23, 25, 27, 30, 33, 36, 39, 41, 45, 49, 51, 53, 56, 59, 61, 65, 67, 69, 72, 75, 77, 81, 83, 88, 91, 94, 98, 100, 102, 105, 107, 111, 113, 116, 119, 121, 123, 126, 129, 134, 136, 138, 142, 144, 147, 149, 152, 155, 158, 161, 163, 165, 168
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| This is the second row of the infinite array a(k,n) = n-th squarefree number + n-th cube-free number + ... + n-th ((k+1)-th) power-free number. The first row a(2,n) gives the squarefree numbers A005117. The 2nd row a(3,n) is the squarefree numbers A005117 + n-th cube-free number A004709. The 3rd row a(4,n) is the squarefree numbers A005117 + n-th cube-free number A004709 + n-th biquadratefree number A046100.
The first 10 columns of the first 4 rows of this array are:
1...2...3...5...6...7..10..11..13, 14
2...4...6...9..11..13..17..20..23..25
3...6...9..13..16..19..24..28..31..35
4...8..12..17..21..25..31..36..40..45
The main diagonal of the array begins 1, 4, 9, 17.
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FORMULA
| a(n) = A005117(n) + A004709(n).
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EXAMPLE
| a(1) = 1+1 = 2.
a(4) = 5+4 = 9.
a(8) = 11+9 = 20.
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CROSSREFS
| Cf. A004709, A005117, A046100.
Sequence in context: A189930 A184627 A203988 * A186220 A186316 A186343
Adjacent sequences: A160810 A160811 A160812 * A160814 A160815 A160816
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KEYWORD
| nonn,easy
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Jan 19 2011
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