login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
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/(1-x^n)) - Joerg Arndt, Jan 30 2011

a(n) = (A000203(n) - A001227(n)) / 2. - Franklin T. Adams-Watters, 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 25 02:23 EDT 2021. Contains 345445 sequences. (Running on oeis4.)