

A086988


Sum of odd indexed divisors of n.


1



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
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OFFSET

1,4


COMMENTS

a(p) = 1 iff p is prime or p=1.


LINKS



EXAMPLE

10 has divisors 1,2,5 and 10. The oddindexed divisors are 1 and 5, so a(10)=6.


MATHEMATICA

Table[Total[Transpose[Partition[Divisors[n], 2, 2, 1]][[1]]], {n, 80}] (* Harvey P. Dale, Apr 21 2011 *)


PROG

(PARI) for (n=1, 100, s=0; c=1; fordiv(i=n, i, c++; if (c%2==0, s+=i)); print1(", "s))


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



