A038688 - OEIS

A038688

Squares that are the sum of the divisors of some number.

1, 4, 36, 121, 144, 256, 324, 400, 576, 784, 900, 961, 1024, 1296, 1600, 1764, 1936, 2304, 2704, 2916, 3136, 3600, 3844, 4096, 4356, 4624, 4900, 5184, 5776, 6084, 6400, 7056, 7744, 8100, 9216, 9604, 10000, 10404, 10816, 11664, 12544, 12996, 14400

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)

Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems: Inversion of Multiplicative Functions (invphi.gp).

FORMULA

a(n) = A228061(n)^2. - Amiram Eldar, Aug 12 2024

MATHEMATICA

nn = 14400; t = Select[Union[DivisorSigma[1, Range[nn]]], IntegerQ[Sqrt[#]] &]; t = Select[t, # <= nn &] (* T. D. Noe, Sep 04 2013 *)

PROG

(PARI) lista(kmax) = for(k = 1, kmax, if(invsigmaNum(k^2) > 0, print1(k^2, ", "))); \\ Amiram Eldar, Aug 12 2024, using Max Alekseyev's invphi.gp

CROSSREFS

Intersection of A000290 and A002191.

Cf. A000203, A006532, A228061.

Sequence in context: A190318 A193874 A254939 * A362751 A076830 A144298

Adjacent sequences: A038685 A038686 A038687 * A038689 A038690 A038691

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved