A366524 Largest square divisor of n which is < sqrt(n), for n >= 2; a(1) = 1.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 1, 1, 4, 1, 9, 1, 4, 1, 1, 1, 4, 1, 1, 9, 4

Offset: 1

Author

Ilya Gutkovskiy, Oct 11 2023

Keywords

• nonn

Links

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

Crossrefs

Cf. A008833, A060775, A366523.

Programs

Mathematica

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

PARI

a(n) = {my(m=1); fordiv(sqrtint(n/core(n)), d, if(d^4 < n, m=max(m,d))); m^2} \\ Andrew Howroyd, Oct 11 2023