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A013642
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Numbers n such that continued fraction for sqrt(n) has period 2.
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2
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3, 6, 8, 11, 12, 15, 18, 20, 24, 27, 30, 35, 38, 39, 40, 42, 48, 51, 56, 63, 66, 68, 72, 80, 83, 84, 87, 90, 99, 102, 104, 105, 110, 120, 123, 132, 143, 146, 147, 148, 150, 152, 156, 168, 171, 182, 195, 198, 200, 203, 210, 224, 227, 228, 230, 231, 235, 240, 255, 258, 260, 264
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| This sequence is identical to the sequence of numbers of the form n = a^2 + b, where a and b are positive integers and b is a factor of 2a greater than 1, in which case the continued fraction expansion of sqrt(n) is [a; [2a/b, 2a]]. - David Terr (David_C_Terr(AT)raytheon.com), Jun 11 2004
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REFERENCES
| Kenneth H. Rosen, Elementary Number Theory and Its Applications, Addison-Wesley, 1984, page 426 (but beware of errors!)
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CROSSREFS
| Cf. A001066 A043549 A026604 A047219 A090848 A004957.
Sequence in context: A043549 A124051 A026604 * A140482 A118011 A189679
Adjacent sequences: A013639 A013640 A013641 * A013643 A013644 A013645
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KEYWORD
| nonn
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AUTHOR
| Clark Kimberling (ck6(AT)evansville.edu)
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