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Search: id:A080806
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| A080806 |
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Positive integer values of n such that 6n^2-5 is a square. |
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7
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| 1, 3, 7, 29, 69, 287, 683, 2841, 6761, 28123, 66927, 278389, 662509, 2755767, 6558163, 27279281, 64919121, 270037043, 642633047, 2673091149, 6361411349, 26460874447, 62971480443, 261935653321, 623353393081, 2592895658763
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The corresponding sequence for which 6n^2-6 is a square is A001079.
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LINKS
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Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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FORMULA
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a(n)=10a(n-2)-a(n-4).
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EXAMPLE
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29 is a term of the sequence since 6*29^2 - 5 = 5041 = 71^2.
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MATHEMATICA
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Do[ If[ IntegerQ[ Sqrt[6n^2 - 5]], Print[n]], {n, 1, 3*10^7}]
a[1]=1; a[2]=3; a[3]=7; a[4]=29; a[n_] := a[n]=10a[n-2]-a[n-4]
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CROSSREFS
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Cf. A001079.
Sequence in context: A038900 A068485 A019352 this_sequence A096064 A110613 A088095
Adjacent sequences: A080803 A080804 A080805 this_sequence A080807 A080808 A080809
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KEYWORD
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nonn
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AUTHOR
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John W. Layman (layman(AT)math.vt.edu), Mar 24 2003
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EXTENSIONS
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Extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 14 2003
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