A065741 Largest square <= sum of squares of divisors of n.

1, 4, 9, 16, 25, 49, 49, 81, 81, 121, 121, 196, 169, 225, 256, 324, 289, 441, 361, 529, 484, 576, 529, 841, 625, 841, 784, 1024, 841, 1296, 961, 1296, 1156, 1444, 1296, 1849, 1369, 1764, 1681, 2209, 1681, 2500, 1849, 2500, 2304, 2601, 2209, 3364, 2401

Offset: 1

Author

Labos Elemer, Nov 15 2001

Keywords

• easy
• nonn

Links

• Harry J. Smith, Table of n, a(n) for n=1..1000

Crossrefs

Cf. A001157, A048760, A065730-A065741.

Programs

Mathematica

Table[Floor[Sqrt[DivisorSigma[2, w]]//N]^2, {w, 1, 100}]

PARI

a(n) = { sqrtint(sigma(n,2))^2 } \\ Harry J. Smith, Oct 29 2009

Formula

a(n) = A048760(A001157(n)).