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A080476
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Floor( geometric mean of next n numbers ).
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4
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1, 2, 4, 8, 12, 18, 24, 32, 40, 50, 60, 72, 84, 98, 112, 128, 144, 162, 180, 200, 220, 242, 264, 288, 312, 338, 364, 392, 420, 450, 480, 512, 544, 578, 612, 648, 684, 722, 760, 800, 840, 882, 924, 968, 1012, 1058, 1104, 1152, 1200, 1250, 1300, 1352, 1404, 1458
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OFFSET
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1,2
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COMMENTS
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Essentially the same as A007590: a(n) = A007590(n) for n>=2.
Also, floor( harmonic mean of next n numbers ).
Also, floor(sqrt(A131479(n)+1)). - Richard R. Forberg, Aug 04 2013
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LINKS
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Table of n, a(n) for n=1..54.
Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1).
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FORMULA
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a(n+3) = 2*a(n+2)-a(n+1) if n even, a(n+3) = 2*a(n+2)-a(n+1)+2 if n odd, with a(1)=1, a(2)=2, a(3)=4. - Yosu Yurramendi, Sep 12 2008
a(n)= 2*a(n-1)-2*a(n-3)+a(n-4) for n>5. G.f.: x*(x^4-2*x^3-1) / ((x-1)^3*(x+1)). - Colin Barker, Aug 08 2013
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EXAMPLE
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a(4) = floor( (7*8*9*10)^(1/4) ) = 8.
a(4) = floor( 1/{ (1/7 + 1/8 + 1/9 + 1/10 )*(1/4)} ) = 8.
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PROG
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(PARI) a(n)=if(n<2, n>0, n^2\2);
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CROSSREFS
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Cf. A000982.
Sequence in context: A337120 A100057 A007590 * A256885 A293495 A330130
Adjacent sequences: A080473 A080474 A080475 * A080477 A080478 A080479
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KEYWORD
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nonn,easy
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AUTHOR
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Amarnath Murthy, Mar 11 2003
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EXTENSIONS
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More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 06 2003
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STATUS
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approved
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