login
A066472
Numbers having exactly six anti-divisors.
1
32, 49, 50, 60, 72, 81, 121, 128, 145, 180, 181, 196, 264, 288, 324, 361, 480, 529, 684, 685, 961, 1156, 1405, 2304, 2401, 2500, 2521, 2704, 2809, 4624, 4705, 5041, 5184, 7396, 8064, 8581, 9385, 10816, 11881, 13456, 14281, 25600, 26569, 27556, 34585
OFFSET
1,1
COMMENTS
See A066272 for definition of anti-divisor.
LINKS
Jon Perry, The Anti-Divisor [broken link; see below]
Jon Perry, The Anti-divisor [Cached copy]
MATHEMATICA
antid[n_] := Select[ Union[ Join[ Select[ Divisors[2n - 1], OddQ[ # ] && # != 1 & ], Select[ Divisors[2n + 1], OddQ[ # ] && # != 1 & ], 2n/Select[ Divisors[ 2*n], OddQ[ # ] && # != 1 &]]] }, # < n & ]]; Select[ Range[10^4], Length[ antid[ # ]] == 6 & ]
PROG
(Python)
from sympy.ntheory.factor_ import antidivisor_count
A066472_list = [n for n in range(1, 10**5) if antidivisor_count(n) == 6] # Chai Wah Wu, Jul 25 2015
CROSSREFS
Cf. A066272.
Sequence in context: A045023 A222300 A259770 * A140172 A259765 A256521
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Jan 02 2002
STATUS
approved