A066470 Numbers having just five anti-divisors.

17, 22, 23, 25, 27, 28, 31, 33, 35, 37, 39, 42, 43, 46, 47, 55, 57, 62, 65, 66, 70, 71, 74, 75, 76, 78, 80, 86, 90, 91, 92, 99, 101, 107, 109, 111, 118, 119, 124, 125, 129, 131, 132, 139, 144, 151, 152, 154, 155, 159, 160, 164, 166, 168, 177, 183, 184, 186, 190

Offset

1,1

Comments

See A066272 for definition of anti-divisor.

Links

Table of n, a(n) for n=1..59.

Jon Perry, The Anti-Divisor

Jon Perry, The Anti-divisor [Cached copy]

Jon Perry, The Anti-divisor: Even More Anti-Divisors [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[ # ]] == 5 & ]

Crossrefs

Cf. A066272.

Sequence in context: A146611 A146398 A146406 * A054478 A136198 A158246

Adjacent sequences: A066467 A066468 A066469 * A066471 A066472 A066473

Keyword

nonn

Author

Robert G. Wilson v, Jan 02 2002

Status

approved