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Search: id:A046655
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| A046655 |
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Sum of the squares of divisors is also a square number:. |
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+0
2
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| 1, 42, 246, 287, 728, 1434, 1673, 1880, 4264, 6237, 9799, 9855, 18330, 21352, 21385, 24856, 36531, 39990, 46655, 57270, 66815, 92664, 125255, 156570, 182665, 208182, 212949, 242879, 273265
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 42, p. 16, Ellipses, Paris 2008.
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LINKS
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M. F. Hasler, Table of n, a(n) for n=1,...,99. [From M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Oct 05 2008]
Project Euler, Problem 211: Divisor Square Sum. [From M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Oct 05 2008]
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EXAMPLE
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a[ 3 ]=246=2*3*41 with 8 divisors: 1,2,3,6,41,82,123,246. The sum of squares of the divisors is 84100=290^2, also a square.
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PROGRAM
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(PARI) for( n=1, 10^6, issquare(sigma(n, 2)) && print1(n", ")) [From M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Oct 05 2008]
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CROSSREFS
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Cf. A046656.
A000290, A001157. [From M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Oct 05 2008]
Sequence in context: A154472 A116004 A122242 this_sequence A156357 A064369 A036463
Adjacent sequences: A046652 A046653 A046654 this_sequence A046656 A046657 A046658
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu)
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