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A081240
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#{(i,j): mu(i)*mu(j) = 1, 1<=i,j<=n}, where mu=A008683 (Moebius function).
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2
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1, 2, 5, 5, 10, 13, 20, 20, 20, 25, 34, 34, 45, 52, 61, 61, 74, 74, 89, 89, 100, 113, 130, 130, 130, 145, 145, 145, 164, 185, 208, 208, 225, 244, 265, 265, 290, 313, 338, 338, 365, 394, 425, 425, 425, 452, 485, 485, 485, 485, 514, 514, 549, 549, 580, 580, 613
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A081238(n) + A081239(n) + a(n) = n^2;
a(n) = a(n-1) iff mu(n) = 0.
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EXAMPLE
| n mu(n) ... n: 1 2 3 4 5 6 7 8
- ------ .... |---------------->
1 .. +1 ..... | + - - 0 - + - 0
2 .. -1 ..... | - + + 0 + - + 0
3 .. -1 ..... | - + + 0 + - + 0
4 ... 0 ..... | 0 0 0 0 0 0 0 0
5 .. -1 ..... | - + + 0 + - + 0 a(8)=20, as there are
6 .. +1 ..... | + - - 0 - + - 0 20 '+1's in the 8x8-square
7 .. -1 ..... | - + + 0 + - + 0 (represented as '+')
8 ... 0 ..... | 0 0 0 0 0 0 0 0.
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CROSSREFS
| Cf. A070548.
Sequence in context: A059797 A173567 A034387 * A184443 A132295 A086651
Adjacent sequences: A081237 A081238 A081239 * A081241 A081242 A081243
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 11 2003
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