A066464 Least number k such that k has n anti-divisors.

1, 3, 5, 7, 13, 17, 32, 38, 85, 67, 162, 137, 338, 203, 760, 247, 1225, 472, 578, 682, 1012, 787, 9112, 1463, 2048, 2047, 2888, 2363, 5513, 3465, 5512, 6682, 8978, 5197, 17672, 5198, 71442, 9653, 29768, 8662, 40898, 13513, 81608, 15593, 131072, 35437

Offset: 0

Author

Robert G. Wilson v, Jan 02 2002

Keywords

• nonn

Comments

See A066272 for definition of anti-divisor.

Links

• Donovan Johnson, Table of n, a(n) for n = 0..400

Crossrefs

Cf. A066272.

Programs

Mathematica

antid[n_] := Select[ Union[ Join[ Select[ Divisors[2n - 1], OddQ[ # ] && # != 1 & ], Select[ Divisors[2n + 1], OddQ[ # ] && # != 1 & ], 2n/Select[ Divisors[ 2n], OddQ[ # ] && # != 1 &]]], # < n & ]; a = Table[0, {50} ]; Do[ b = Length[ antid[n]]; If[ b < Length[a] && a[[b + 1]] == 0, a[[b + 1]] = n], {n, 1, 2^17} ]; a