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A068716
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x^2 + 1 = n * y^2 has infinitely many solutions in integers (x,y).
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2
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0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| H. Davenport, The Higher Arithmetic. Cambridge Univ. Press, 7th ed., 1999, table 1.
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LINKS
| John Robertson, Solving x^2-dy^2=+-1.
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FORMULA
| a(n)= 1 - (A067280(n) mod 2 ).
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EXAMPLE
| a(2)= 1: x*x + 1 = 2 * y*y is soluble, e.g. 7*7 + 1= 2*5*5.
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CROSSREFS
| Cf. A068717, A067280, A006702, A006703.
Sequence in context: A106701 A033684 A080885 * A179828 A129185 A129184
Adjacent sequences: A068713 A068714 A068715 * A068717 A068718 A068719
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KEYWORD
| nonn
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AUTHOR
| Frank.Ellermann(AT)t-online.de, Feb 25 2002
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EXTENSIONS
| More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 31 2003
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