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A038688
Squares that are the sum of the divisors of some number.
4
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
OFFSET
1,2
LINKS
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.
Sequence in context: A190318 A193874 A254939 * A362751 A076830 A144298
KEYWORD
nonn
STATUS
approved