

A086670


Sum of floor(d/2) where d is a divisor of n.


0



0, 1, 1, 3, 2, 5, 3, 7, 5, 8, 5, 13, 6, 11, 10, 15, 8, 18, 9, 20, 14, 17, 11, 29, 14, 20, 18, 27, 14, 34, 15, 31, 22, 26, 22, 44, 18, 29, 26, 44, 20, 46, 21, 41, 36, 35, 23, 61, 27, 45, 34, 48, 26, 58, 34, 59, 38, 44, 29, 82, 30, 47, 49, 63, 40, 70, 33, 62, 46, 70, 35, 96, 36, 56
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OFFSET

1,4


COMMENTS

Inverse Mobius transform of A004526. [From R. J. Mathar, Jan 19 2009]


LINKS

Table of n, a(n) for n=1..74.


FORMULA

G.f.: sum(n>=1, floor(n/2)*x^n/(1x^n))  Joerg Arndt, Jan 30 2011
a(n) = (A000203(n)  A001227(n)) / 2.  Franklin T. AdamsWatters, Jan 05 2012.


EXAMPLE

10 has divisors 1,2,5,10. floor(d/2) gives 0,1,2,5, therefore a(10)=8.


PROG

(PARI) for (n=1, 100, s=0; fordiv(i=n, i, s+=floor(i/2)); print1(", "s))


CROSSREFS

Sequence in context: A083242 A111618 A107128 * A075888 A075889 A181771
Adjacent sequences: A086667 A086668 A086669 * A086671 A086672 A086673


KEYWORD

nonn


AUTHOR

Jon Perry, Jul 27 2003


STATUS

approved



