OFFSET
1,3
COMMENTS
Appears to be the determinant of n X n (-1,1) matrix defined by A(i,j)=1 if j=1 or i divides j else -1.
Appears also to be the determinant of n X n (-i/j,i/j) matrix defined by A(i,j)=i/j if j=1 or i divides j else -i/j.
FORMULA
a(n) = 2^(n-1)*A002321(n). - Chai Wah Wu, Mar 30 2021
PROG
(Python)
from functools import lru_cache
@lru_cache(maxsize=None)
def A162459(n):
if n == 0:
return 0
c, j = n, 2
k1 = n//j
while k1 > 1:
j2 = n//k1 + 1
c += (j2-j)*A162459(k1)//2**(k1-1)
j, k1 = j2, n//j2
return 2**(n-1)*(j-c) # Chai Wah Wu, Mar 30 2021
CROSSREFS
KEYWORD
sign
AUTHOR
Mats Granvik, Jul 04 2009
STATUS
approved