OFFSET
0,2
COMMENTS
The sequence A006218 : Sum_{i=1..n} floor(n/i) = Sum_{i=1..n} sigma_0(i). Sigma_0(i) is A000005. Sequences of the type : Sum_{i=1..f(n)} floor(f(n)/i)= Sum_{i=1..f(n)} sigma_0(i). This sequence a(n)= A006218(2*n). [Ctibor O. Zizka, Mar 21 2009]
For n > 0: row sums of the triangle in A013942. - Reinhard Zumkeller, Jun 04 2013
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
MATHEMATICA
Table[Total[Floor[2*n/Range[2*n]]], {n, 0, 100}] (* T. D. Noe, Jun 12 2013 *)
PROG
(Haskell)
a062550 0 = 0
a062550 n = sum $ a013942_row n -- Reinhard Zumkeller, Jun 04 2013
(Python)
from math import isqrt
def A062550(n): return (lambda m: 2*sum(2*n//k for k in range(1, m+1))-m*m)(isqrt(2*n)) # Chai Wah Wu, Oct 09 2021
(PARI) a(n) = sum(k=1, 2*n, (2*n)\k); \\ Michel Marcus, Oct 09 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Henry Bottomley, Jun 26 2001
EXTENSIONS
Data corrected for n > 30 by Reinhard Zumkeller, Jun 04 2013
STATUS
approved