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A207375
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Irregular array read by rows in which row n lists the (one or two) central divisors of n in increasing order.
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43
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1, 1, 2, 1, 3, 2, 1, 5, 2, 3, 1, 7, 2, 4, 3, 2, 5, 1, 11, 3, 4, 1, 13, 2, 7, 3, 5, 4, 1, 17, 3, 6, 1, 19, 4, 5, 3, 7, 2, 11, 1, 23, 4, 6, 5, 2, 13, 3, 9, 4, 7, 1, 29, 5, 6, 1, 31, 4, 8, 3, 11, 2, 17, 5, 7, 6, 1, 37, 2, 19, 3, 13, 5, 8, 1, 41, 6, 7, 1, 43
(list;
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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COMMENTS
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If n is a square then row n lists only the square root of n because the squares (A000290) have only one central divisor.
If n is not a square then row n lists the pair (j, k) of divisors of n, nearest to the square root of n, such that j*k = n.
Conjecture 1: It appears that the n-th record in this sequence is the last member of row A008578(n).
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LINKS
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EXAMPLE
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Array begins:
1;
1, 2;
1, 3;
2;
1, 5;
2, 3;
1, 7;
2, 4;
3;
2, 5;
1, 11;
3, 4;
1, 13;
...
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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