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A075861
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Least k such that (n-k) divides (n+k).
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0
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1, 1, 2, 3, 2, 5, 4, 3, 5, 9, 4, 11, 7, 5, 8, 15, 6, 17, 10, 7, 11, 21, 8, 15, 13, 9, 14, 27, 10, 29, 16, 11, 17, 21, 12, 35, 19, 13, 20, 39, 14, 41, 22, 15, 23, 45, 16, 35, 25, 17, 26, 51, 18, 33, 28, 19, 29, 57, 20, 59, 31, 21, 32, 39, 22, 65, 34, 23, 35, 69, 24, 71, 37, 25, 38
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,3
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FORMULA
| sum(i=1, n, a(i)) is asymptotic to c*n^2 where c=0.28....
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MATHEMATICA
| Table[i=1; While[!Divisible[n+i, n-i], i++]; i, {n, 2, 100}] (* From Harvey P. Dale, Mar 28 2011 *)
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PROG
| (PARI) a(n)=if(n<0, 0, s=1; while((n+s)%(n-s)>0, s++); s)
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CROSSREFS
| Sequence in context: A011153 A132226 A197702 * A205706 A141658 A089587
Adjacent sequences: A075858 A075859 A075860 * A075862 A075863 A075864
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 15 2002
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