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Search: id:A006532
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| A006532 |
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Numbers n such that sum of divisors is a square.
(Formerly M3089)
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+0
15
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| 1, 3, 22, 66, 70, 81, 94, 115, 119, 170, 210, 214, 217, 265, 282, 310, 322, 343, 345, 357, 364, 382, 385, 400, 472, 497, 510, 517, 527, 642, 651, 679, 710, 742, 745, 782, 795, 820, 862, 884, 889, 930, 935, 966, 970, 1004, 1029, 1066, 1080, 1092, 1146
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 8.
D. Wells, Curious and interesting numbers, Penguin Books, p. 111.
J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 94, p. 33, Ellipses, Paris 2008.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
Index entries for sequences related to sums of squares
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MAPLE
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for i from 1 to 1000 do if issqr(sigma(i)) then print(i); fi; od;
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MATHEMATICA
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Select[ Range[ 1150 ], IntegerQ[ Sqrt[ DivisorSigma[ 1, # ] ] ]& ]
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CROSSREFS
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Sequence in context: A041103 A104604 A139272 this_sequence A005288 A055550 A075204
Adjacent sequences: A006529 A006530 A006531 this_sequence A006533 A006534 A006535
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KEYWORD
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easy,nonn,nice
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AUTHOR
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njas, Simon Plouffe (plouffe(AT)math.uqam.ca)
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EXTENSIONS
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Additional reference from Felice Russo (felice.russo(AT)katamail.com). More terms from Enoch Haga (Enokh(AT)comcast.net).
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