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A106331
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Numbers j such that 24*(j^2) + 25 = k^2.
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2
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0, 1, 2, 5, 12, 21, 50, 119, 208, 495, 1178, 2059, 4900, 11661, 20382, 48505, 115432, 201761, 480150, 1142659, 1997228, 4752995, 11311158, 19770519, 47049800, 111968921, 195707962, 465745005, 1108378052, 1937309101, 4610400250
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OFFSET
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1,3
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COMMENTS
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The ratio k(n) /(2*j(n)) tends to sqrt(6) as n increases
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LINKS
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FORMULA
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j(1)=0, j(2)=1, j(3)=2, j(4)=5, j(5)=10*j(2)+j(3), j(6)=10*j(3)+j(2), j(7)=10*j(4)+j(1) then j(n)=10*j(n-3)-j(n-6).
a(n) = +10*a(n-3) -a(n-6). G.f.: x^2*(1+2*x+5*x^2+2*x^3+x^4)/(1-10*x^3+x^6). [R. J. Mathar, May 22 2010]
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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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STATUS
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approved
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