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A190350
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Define a series of lists by L_1 = [1], L_{k+1} = [i+1, i^2+i+1 : i in L_k]; then a(n) = numerator of Sum (1/i : i in L_n).
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1
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OFFSET
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1,2
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COMMENTS
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Sum (1/i : i in L_n) converges to Pi/4 as n -> oo.
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REFERENCES
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J. Borwein, D. Bailey and R. Girgensohn, Experimentation in Mathematics: Computational Paths to Discovery, Peters, Boston, 2004. See Sect. 1.3.
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LINKS
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EXAMPLE
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1, 5/6, 877/1092, 3349607/4218760, 21942759935479332971926241/27765973216255750329906360, ...
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MAPLE
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M:=6; s1:={1}; n1[1]:=1;
for n from 2 to M do
s2:={};
for i in s1 do s2:={op(s2), i+1, i^2+i+1 }; od:
n1[n] := add(1/i, i in s2):
s1:=s2;
od:
s3:=[seq(n1[i], i=1..M)];
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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