A066482 The smallest anti-divisor of n.

2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 8, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 8, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 64, 2, 3, 2, 3

Offset

3,1

Comments

Almost identical to A007978, least non-divisor of n, but there are some subtle differences.

See A066272 for definition of anti-divisor.

Links

Seiichi Manyama, Table of n, a(n) for n = 3..10000

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 & ]; Table[ First[ antid[n]], {n, 3, 100} ]

Crossrefs

Cf. A066481.

Sequence in context: A127237 A340218 A199968 * A324507 A123725 A089080

Adjacent sequences: A066479 A066480 A066481 * A066483 A066484 A066485

Keyword

nonn

Author

Robert G. Wilson v, Jan 02 2002

Status

approved