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A145607
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Numbers k such that (3*(2*k + 1)^2 + 2)/5 is a square.
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2
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0, 4, 35, 279, 2200, 17324, 136395, 1073839, 8454320, 66560724, 524031475, 4125691079, 32481497160, 255726286204, 2013328792475, 15850904053599, 124793903636320, 982500325036964, 7735208696659395, 60899169248238199
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OFFSET
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1,2
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COMMENTS
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Square roots of (3*(2*k+1)^2+2)/5 are listed in A070997, therefore (3*(2*a(n) + 1)^2 + 2)/5 = A070997(n-1)^2.
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LINKS
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FORMULA
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a(n+2) = 8*a(n+1) - a(n) + 3.
G.f.: x^2*(4 - x)/((1 - x)*(1 - 8*x + x^2)).
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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a(4) corrected, extended, definition corrected by R. J. Mathar, Oct 24 2008
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STATUS
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approved
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