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!)
A339370 a(n) = Sum_{k=1..floor(n/2)} (n-k) * floor((n-k)/k). 3
0, 1, 4, 11, 19, 36, 50, 76, 102, 138, 165, 227, 262, 318, 381, 460, 510, 614, 672, 791, 889, 990, 1064, 1249, 1353, 1477, 1610, 1790, 1891, 2133, 2244, 2455, 2626, 2798, 2983, 3312, 3452, 3649, 3857, 4198, 4356, 4715, 4883, 5190, 5514, 5763, 5949, 6446, 6686, 7045 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Total area of all y X z rectangles such that x + y = n, with x and y integers, 0 < x <= y and z = floor(y/x). - Wesley Ivan Hurt, Dec 21 2020

LINKS

Table of n, a(n) for n=1..50.

FORMULA

a(n) ~ n^2*(log(n) + 2*EulerGamma - Pi^2/12 - 3/2). - Rok Cestnik, Dec 20 2020

a(n) = n*A002541(n) - A153485(n). - Vaclav Kotesovec, Dec 21 2020

MATHEMATICA

Table[Sum[(n - k)*Floor[(n - k)/k], {k, Floor[n/2]}], {n, 60}]

PROG

(PARI) a(n) = sum(k=1, n\2, (n-k) * ((n-k)\k)); \\ Michel Marcus, Dec 02 2020

CROSSREFS

Cf. A002541, A153485.

Sequence in context: A102788 A016433 A049841 * A038439 A038431 A009908

Adjacent sequences:  A339367 A339368 A339369 * A339371 A339372 A339373

KEYWORD

nonn,easy

AUTHOR

Wesley Ivan Hurt, Dec 01 2020

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 August 2 02:53 EDT 2021. Contains 346409 sequences. (Running on oeis4.)