A063831 Sum of cubes of divisors is a square.

1, 2, 345, 690, 47196, 46248900, 53262468, 71315748, 140553735, 188194335, 215515727, 281107470, 288564647, 292978595, 310129096, 376388670, 431031454, 577129294, 585957190, 1474108335, 2133051720, 2489605188, 2948216670, 3270679304, 4043104611, 5142743032

Offset

1,2

Links

Table of n, a(n) for n=1..26.

Example

345 is in the sequence since sigma_3(345) = 6552^2 is a square.

Mathematica

Select[Range[10^5], IntegerQ[ Sqrt[ DivisorSigma[3, #] ] ] &] (* Amiram Eldar, Dec 06 2018 *)

Prog

(PARI) for(n=1, 10^5, if(issquare(sigma(n, 3)), print1(n, ", ")))

Crossrefs

Cf. A001158, A006532, A046655.

Sequence in context: A172136 A248172 A064501 * A216356 A064023 A370483

Adjacent sequences: A063828 A063829 A063830 * A063832 A063833 A063834

Keyword

nonn

Author

Jason Earls, Aug 21 2001

Extensions

More terms from Thomas Baruchel, Oct 20 2003

More terms from Sean A. Irvine, Sep 24 2009

a(24)-a(26) from Amiram Eldar, Dec 06 2018

Status

approved