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Search: id:A125844
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| A125844 |
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a(n) = the smallest positive integer which does not occur earlier in the sequence and which is coprime to the n-th composite integer. |
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+0
1
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| 1, 5, 3, 2, 7, 11, 9, 4, 13, 17, 19, 8, 15, 23, 6, 21, 10, 25, 29, 27, 14, 31, 12, 35, 33, 16, 37, 41, 39, 22, 43, 47, 18, 49, 20, 45, 53, 24, 51, 26, 55, 59, 57, 32, 61, 28, 65, 63, 34, 67, 71, 69, 38, 73, 30, 77, 79, 40, 75, 83, 36, 81, 44, 85, 89, 46, 87, 50, 91, 42, 95, 93
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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This sequence is a permutation of the positive integers.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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The positive integers which do not occur among the first 6 terms of the sequence are 4,6,8,9,10,12,... Of these integers, 9 is the smallest that is coprime to 14, the 7th composite. So a(7) = 9.
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MATHEMATICA
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f[l_List] := Block[{n = Length[l] + 1, c = 1, k = n}, While[k > 0, c++; While[PrimeQ[c], c++ ]; k--; ]; k = 1; While[MemberQ[l, k] || GCD[k, c] > 1, k++ ]; Append[l, k]]; Nest[f, {}, 75] (*Chandler*)
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CROSSREFS
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Cf. A002808.
Sequence in context: A165102 A009661 A023576 this_sequence A065627 A064812 A068118
Adjacent sequences: A125841 A125842 A125843 this_sequence A125845 A125846 A125847
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Feb 03 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 07 2007
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