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Search: id:A122212
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| A122212 |
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a(n) = n-th integer from among those positive integers which are coprime to the sum of the divisors of n. |
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+0
3
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| 1, 2, 5, 4, 13, 17, 13, 14, 9, 29, 31, 27, 29, 41, 43, 16, 49, 29, 47, 67, 41, 65, 67, 89, 25, 89, 67, 65, 107, 89, 61, 55, 97, 101, 103, 45, 77, 139, 89, 149, 143, 125, 93, 151, 145, 137, 139, 99, 77, 77, 151, 121, 157, 199, 163, 209, 141, 217, 221, 209, 125, 185, 135
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OFFSET
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1,2
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EXAMPLE
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8 = 1 + 7 is the sum of the divisors of 7. 1,3,5,7,9,11,13,15,17,19,21...are the positive integers which are
coprime to 8. Of these integers, 13 is the 7th. So a(7) = 13.
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MATHEMATICA
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f[n_] := Block[{c = n, k = 0}, While[c > 0, k++; While[GCD[DivisorSigma[1, n], k] > 1, k++ ]; c-- ]; k ]; Table[f[n], {n, 63}] (*Chandler*)
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CROSSREFS
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Cf. A122213.
Adjacent sequences: A122209 A122210 A122211 this_sequence A122213 A122214 A122215
Sequence in context: A084410 A080067 A117824 this_sequence A102468 A079053 A002518
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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), Aug 26 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Aug 29 2006
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