A366520 Largest odd divisor of n which is < sqrt(n), for n >= 2; a(1) = 1.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 5, 1, 1, 3, 1, 5, 3, 1, 1, 3, 5, 1, 3, 1, 1, 5, 1, 1, 3, 1, 5, 3, 1, 1, 3, 5, 7, 3, 1, 1, 5, 1, 1, 7, 1, 5, 3, 1, 1, 3, 7, 1, 3, 1, 1, 5, 1, 7, 3, 1, 5, 3, 1, 1, 7, 5, 1, 3, 1, 1, 9, 7, 1, 3, 1, 5, 3, 1, 7, 9, 5

Offset: 1

Author

Ilya Gutkovskiy, Oct 11 2023

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000265, A060775, A093803, A366519.

Programs

Mathematica

Join[{1}, Table[Last[Select[Divisors[n], # < Sqrt[n] && OddQ[#] &]], {n, 2, 100}]]

PARI

a(n) = {my(m=1); fordiv(n/2^valuation(n,2), d, if(d^2 < n, m=max(m,d))); m} \\ Andrew Howroyd, Oct 11 2023