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A210208
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Triangle read by rows in which row n lists the divisors of n that are prime powers, A000961.
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9
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1, 1, 2, 1, 3, 1, 2, 4, 1, 5, 1, 2, 3, 1, 7, 1, 2, 4, 8, 1, 3, 9, 1, 2, 5, 1, 11, 1, 2, 3, 4, 1, 13, 1, 2, 7, 1, 3, 5, 1, 2, 4, 8, 16, 1, 17, 1, 2, 3, 9, 1, 19, 1, 2, 4, 5, 1, 3, 7, 1, 2, 11, 1, 23, 1, 2, 3, 4, 8, 1, 5, 25, 1, 2, 13, 1, 3, 9, 27, 1, 2, 4, 7
(list;
graph;
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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LINKS
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Eric Weisstein's World of Mathematics, Divisor
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EXAMPLE
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1;
1, 2;
1, 3;
1, 2, 4;
1, 5;
1, 2, 3;
1, 7;
1, 2, 4, 8;
1, 3, 9;
1, 2, 5;
1, 11;
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MATHEMATICA
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Table[Prepend[Select[Divisors[n], PrimeNu[#] == 1 &], 1], {n, 1, 10}]//Grid (* Geoffrey Critzer, Feb 08 2015 *)
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PROG
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(Haskell)
a210208 n k = a210208_tabf !! (n-1) !! (n-1)
a210208_row n = a210208_tabf !! (n-1)
a210208_tabf = map (filter ((== 1) . a010055)) a027750_tabf
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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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