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A161901
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Array read by rows in which row n lists the divisors of n, but if n is a square then the square root of n appears twice.
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9
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1, 1, 1, 2, 1, 3, 1, 2, 2, 4, 1, 5, 1, 2, 3, 6, 1, 7, 1, 2, 4, 8, 1, 3, 3, 9, 1, 2, 5, 10, 1, 11, 1, 2, 3, 4, 6, 12, 1, 13, 1, 2, 7, 14, 1, 3, 5, 15, 1, 2, 4, 4, 8, 16, 1, 17, 1, 2, 3, 6, 9, 18, 1, 19, 1, 2, 4, 5, 10, 20, 1, 3, 7, 21
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listen;
history;
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OFFSET
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1,4
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COMMENTS
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LINKS
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EXAMPLE
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Array begins:
....... 1,1;
....... 1,2;
....... 1,3;
..... 1,2,2,4;
....... 1,5;
..... 1,2,3,6;
....... 1,7;
..... 1,2,4,8;
..... 1,3,3,9;
..... 1,2,5,10;
....... 1,11;
... 1,2,3,4,6,12;
....... 1,13;
..... 1,2,7,14;
..... 1,3,5,15;
... 1,2,4,4,8,16;
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MATHEMATICA
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dsr[n_]:=If[IntegerQ[Sqrt[n]], Sort[Join[{Sqrt[n]}, Divisors[n]]], Divisors[ n]]; Array[ dsr, 30]//Flatten (* Harvey P. Dale, Sep 27 2020 *)
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CROSSREFS
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KEYWORD
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easy,nonn,tabf
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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