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Search: id:A126638
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| A126638 |
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a(n) is larger than a(n-1), not prime and coprime to a(n-1) and a(n-2). |
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1
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| 4, 9, 25, 26, 27, 35, 38, 39, 49, 50, 51, 77, 80, 81, 91, 92, 93, 95, 98, 99, 115, 116, 117, 119, 121, 122, 123, 125, 128, 129, 133, 134, 135, 143, 146, 147, 155, 158, 159, 161, 164, 165, 169, 172, 175, 177, 178, 185, 187, 188, 189, 205, 206, 207, 209, 212, 213
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(7) = 38 bacause it is the next composite number larger than 35 (a(6)) that shares no factors in common with 35 and 27 (a(5)).
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MAPLE
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with(numtheory); i:=4; j:=9; k:=10; while(k < 100) do while(order(k, i) = FAIL or order(k, j) = FAIL or isprime(k)) do k:=k+1; end do; print(k); i:= j; j:=k; k:=k+1; end do;
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MATHEMATICA
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f[l_List] := Block[{k = l[[ -1]] + 1}, While[PrimeQ[k] || GCD[k, l[[ -1]]*l[[ -2]]] > 1, k++ ]; Append[l, k]]; Nest[f, {4, 9}, 56] (*Chandler*)
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CROSSREFS
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Cf. A051884.
Sequence in context: A131826 A051961 A093867 this_sequence A073045 A045967 A163836
Adjacent sequences: A126635 A126636 A126637 this_sequence A126639 A126640 A126641
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KEYWORD
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nonn
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AUTHOR
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Ben Thurston (benthurston27(AT)yahoo.com), Feb 08 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 14 2007
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