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A066968
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Denominators of b(n) = 1/16^n*(4/(8*n+1)-2/(8*n+4)-1/(8*n+5)-1/(8*n+6)).
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2
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15, 6552, 5026560, 15590400, 4561108992, 244729774080, 15293220913152, 6027885936640, 2292288470384640, 143113842220597248, 2278611404728565760, 39351244081172840448, 3515953192213728460800, 2551413037895138672640
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| B. Gourevitch, L'univers de Pi
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FORMULA
| sum( k>=0, b(k) ) = Pi
a(n)=denominator((1/16)^n*sum(i=1,4,((-1)^(ceil(4/(2*i))))*(floor(4/i))/(8*n+i+floor(sqrt(i-1))*(floor(sqrt(i-1))+1)))) [From Alexander R. Povolotsky (pevnev(AT)juno.com), Aug 31 2009]
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PROG
| (PARI) a(n)=denominator(1/16^n*(4/(8*n+1)-2/(8*n+4)-1/(8*n+5)-1/(8*n+6)))
(PARI) a(n)=denominator((1/16)^n*sum(i=1, 4, ((-1)^(ceil(4/(2*i))))*(floor(4/i))/(8*n+i+floor(sqrt(i-1))*(floor(sqrt(i-1))+1)))) [From Alexander R. Povolotsky (pevnev(AT)juno.com), Aug 31 2009]
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CROSSREFS
| Cf. A048581.
Sequence in context: A206360 A204677 A198250 * A113795 A205155 A205304
Adjacent sequences: A066965 A066966 A066967 * A066969 A066970 A066971
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KEYWORD
| easy,frac,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 13 2002
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