A066468 Numbers having just three anti-divisors.

7, 10, 11, 14, 15, 19, 20, 21, 26, 29, 30, 34, 44, 48, 51, 54, 56, 69, 79, 89, 106, 114, 120, 134, 141, 146, 156, 174, 191, 216, 224, 244, 251, 271, 296, 309, 316, 321, 359, 376, 384, 386, 394, 404, 411, 439, 496, 516, 524, 596, 601, 614, 659, 664, 691, 719

Offset

1,1

Comments

See A066272 for definition of anti-divisor.

Links

Table of n, a(n) for n=1..56.

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[ # ]] == 3 & ]

Crossrefs

Cf. A066272.

Sequence in context: A191875 A194418 A094764 * A347393 A088769 A057986

Adjacent sequences: A066465 A066466 A066467 * A066469 A066470 A066471

Keyword

nonn

Author

Robert G. Wilson v, Jan 02 2002

Status

approved