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A095167
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Triangle read by rows in which the n-th row contains n numbers noncoprime to n and not occurring in earlier rows.
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7
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1, 2, 4, 3, 6, 9, 8, 10, 12, 14, 5, 15, 20, 25, 30, 16, 18, 21, 22, 24, 26, 7, 28, 35, 42, 49, 56, 63, 32, 34, 36, 38, 40, 44, 46, 48, 27, 33, 39, 45, 51, 54, 57, 60, 66, 50, 52, 55, 58, 62, 64, 65, 68, 70, 72, 11, 77, 88, 99, 110, 121, 132, 143, 154, 165, 176, 69, 74, 75, 76
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OFFSET
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1,2
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COMMENTS
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Rearrangement of natural numbers so that next n numbers are not coprime to n.
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LINKS
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EXAMPLE
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1
2 4
3 6 9
8 10 12 14
5 15 20 25 30
16 18 21 22 24 26
7 28 35 42 49 56 63
...
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MATHEMATICA
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Fold[Function[{a, n}, Join[a, Select[Complement[Range[Max[a] + n^2], a], GCD[n, #] > 1 &, n]]], {1}, Range[2, 12]] (* Ivan Neretin, Jun 05 2015 *)
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PROG
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(PARI) S=Set(); for(n=2, 20, k=0; m=1; while(k<n, m++; if(!setsearch(S, m)&&gcd(m, n)>1, S=setunion(S, [m]); print1(" ", m); k++))) (Alekseyev)
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CROSSREFS
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Cf. A081964 (coprime instead of non-coprime).
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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