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A086988
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Sum of odd indexed divisors of n.
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1
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1, 1, 1, 5, 1, 4, 1, 5, 10, 6, 1, 10, 1, 8, 6, 21, 1, 13, 1, 15, 8, 12, 1, 22, 26, 14, 10, 19, 1, 25, 1, 21, 12, 18, 8, 58, 1, 20, 14, 33, 1, 32, 1, 27, 21, 24, 1, 46, 50, 31, 18, 31, 1, 40, 12, 41, 20, 30, 1, 64, 1, 32, 29, 85, 14, 48, 1, 39, 24, 51, 1, 73, 1, 38, 31, 43, 12, 56, 1, 69
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| a(p)=1 iff p is prime or p=1
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EXAMPLE
| 10 has divisors 1,2,5 and 10. The even indices yield 1 and 15, so a(10)=6
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MATHEMATICA
| Table[Total[Transpose[Partition[Divisors[n], 2, 2, 1]][[1]]], {n, 80}] (* From Harvey P. Dale, Apr 21 2011 *)
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PROG
| (PARI) for (n=1, 100, s=0; c=-1; fordiv(i=n, i, c++; if (c%2==0, s+=i)); print1(", "s))
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CROSSREFS
| Cf. A086989.
Sequence in context: A023138 A194704 A108170 * A010132 A033988 A200421
Adjacent sequences: A086985 A086986 A086987 * A086989 A086990 A086991
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KEYWORD
| nonn
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AUTHOR
| Jon Perry (perry(AT)globalnet.co.uk), Jul 27 2003
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