OFFSET
1,3
COMMENTS
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
n=63 has A000005(63)=6 divisors: 1='1', 3='11', 7='111', 9='1001', 21='10101' and 63='111111', {1,11,111,111111} are also suffixes of 111111, therefore a(63)=4.
MATHEMATICA
a[n_] := DivisorSum[n, 1 &, Mod[n, 2^BitLength[#]] == # &]; Array[a, 100] (* Amiram Eldar, Apr 07 2023 *)
PROG
(Haskell)
import Data.List (isPrefixOf); import Data.Function (on)
a080942 n = length $
filter ((flip isPrefixOf `on` a030308_row) n) $ a027750_row n
-- Reinhard Zumkeller, Mar 27 2014
(Python)
from sympy import divisors
def A080942(n): return sum(1 for d in divisors(n, generator=True) if not (d^n)&((1<<d.bit_length())-1)) # Chai Wah Wu, Jun 20 2023
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Feb 25 2003
STATUS
approved