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A093335
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a(0) = 1, a(1) = 1 and for n >= 2, a(n) = floor(4 * a(n-2) * a(n-1) / (a(n-2) + a(n-1))).
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3
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1, 1, 2, 2, 4, 5, 8, 12, 19, 29, 45, 70, 109, 170, 265, 414, 646, 1009, 1575, 2460, 3840, 5997, 9364, 14622, 22833, 35654, 55676, 86940, 135762, 211998, 331047, 516946, 807239, 1260545, 1968408, 3073772, 4799858, 7495231, 11704199, 18276724
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OFFSET
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0,3
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LINKS
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EXAMPLE
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a(5) = 5 because a(5) = floor(4*a(3)*a(4)/(a(3)+a(4))) = floor(4*2*4/(2+4)) = floor(32/6) = 5.
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MATHEMATICA
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nxt[{a_, b_}]:={b, Floor[2*HarmonicMean[{a, b}]]}; Join[{1}, Transpose[ NestList[ nxt, {1, 2}, 40]][[1]]] (* Harvey P. Dale, Mar 04 2015 *)
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CROSSREFS
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KEYWORD
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easy,nonn,changed
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AUTHOR
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Robert A. Stump (rstump_2004(AT)yahoo.com), Apr 25 2004
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EXTENSIONS
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STATUS
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approved
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