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A085599
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Number of pairs of coprimes (n-i,n+i), 0<i<n.
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0
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0, 0, 1, 1, 2, 1, 3, 3, 3, 3, 5, 3, 6, 5, 4, 7, 8, 5, 9, 7, 6, 9, 11, 7, 10, 11, 9, 11, 14, 7, 15, 15, 10, 15, 12, 11, 18, 17, 12, 15, 20, 11, 21, 19, 12, 21, 23, 15, 21, 19, 16, 23, 26, 17, 20, 23, 18, 27, 29, 15, 30, 29, 18, 31, 24, 19, 33, 31, 22, 23, 35, 23, 36, 35, 20
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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EXAMPLE
| n=7: (7-1,7+1)=(6,8), (7-2,7+2)=(5,9), (7-3,7+3)=(4,10),
(7-4,7+4)=(3,11), (7-5,7+5)=(2,12), (7-6,7+6)=(1,13): only three are
coprime: (5,9), (3,11) and (1,13), therefore a(7)=3.
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CROSSREFS
| Sequence in context: A125087 A111353 A038565 * A110425 A174257 A105637
Adjacent sequences: A085596 A085597 A085598 * A085600 A085601 A085602
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 06 2003
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