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A136178
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Irregular array read by rows: row n contains the GCDs of each pair of consecutive positive divisors of n.
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3
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1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 2, 4, 1, 3, 1, 1, 5, 1, 1, 1, 1, 2, 6, 1, 1, 1, 7, 1, 1, 5, 1, 2, 4, 8, 1, 1, 1, 3, 3, 9, 1, 1, 2, 1, 5, 10, 1, 1, 7, 1, 1, 11, 1, 1, 1, 1, 2, 2, 4, 12, 1, 5, 1, 1, 13, 1, 3, 9, 1, 2, 1, 7, 14, 1, 1, 1, 1, 1, 2, 5, 15, 1, 1, 2, 4, 8, 16, 1, 1, 11, 1, 1, 17, 1, 1, 7, 1, 1, 1, 2, 3
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,4
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COMMENTS
| Each row has d(n)-1 terms, where d(n) is the number of positive divisors of n. The first row listed is row 2.
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EXAMPLE
| The positive divisors of 20 are 1,2,4,5,10,20. GCD(1,2)=1. GCD(2,4)=2. GCD(4,5)=1. GCD(5,10)=5. And GCD(10,20)=10. So row 20 is (1,2,1,5,10).
Contribution from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 20 2009: (Start)
The table starts
1
1
1,2
1
1,1,3
1
1,2,4
1,3
1,1,5
1
1,1,1,2,6
(End)
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MAPLE
| A136178row := proc(n) local dvs; dvs := sort(convert(numtheory[divisors](n), list)) ; seq(gcd(op(d-1, dvs), op(d, dvs)), d=2..nops(dvs)) ; end: seq(A136178row (n), n=1..70) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 20 2009]
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CROSSREFS
| Cf. A136179, A136180, A136181.
Sequence in context: A164306 A111603 A180178 * A047140 A047150 A102054
Adjacent sequences: A136175 A136176 A136177 * A136179 A136180 A136181
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KEYWORD
| nonn,tabf
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AUTHOR
| Leroy Quet, Dec 19 2007
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EXTENSIONS
| Keyword:tabl replaced by keyword:tabf - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 22 2009
Extended beyond row 10 by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 20 2009
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