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

1,2

Links

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

Formula

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

Mathematica

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

Prog

(PARI) sigma2(n)= { local(d, s=0); d=divisors(n); for(i=1, length(d), s+=d[i]^2); return(s) } { for (n=1, 1000, a=sqrtint(sigma2(n))^2; write("b065741.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 29 2009

Crossrefs

Cf. A001157, A048760, A065730-A065741.

Sequence in context: A352048 A206920 A108612 * A188061 A279456 A069560

Adjacent sequences: A065738 A065739 A065740 * A065742 A065743 A065744

Keyword

easy,nonn

Author

Labos Elemer, Nov 15 2001

Status

approved