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A019425
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Continued fraction for tan(1/2).
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3
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0, 1, 1, 4, 1, 8, 1, 12, 1, 16, 1, 20, 1, 24, 1, 28, 1, 32, 1, 36, 1, 40, 1, 44, 1, 48, 1, 52, 1, 56, 1, 60, 1, 64, 1, 68, 1, 72, 1, 76, 1, 80, 1, 84, 1, 88, 1, 92, 1, 96, 1, 100, 1, 104, 1, 108, 1, 112, 1, 116, 1, 120, 1, 124, 1, 128, 1, 132, 1, 136, 1, 140, 1, 144, 1, 148, 1, 152, 1, 156, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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LINKS
| Harry J. Smith, Table of n, a(n) for n=0,...,20000
G. Xiao, Contfrac
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FORMULA
| a(n)=n-1/2-(n-3/2)*(-1)^n+C(1,n)-2*C(0,n); - Paul Barry (pbarry(AT)wit.ie), Oct 25 2007
a(n)=2*a(n-2)-a(n-4), n>=6 . G.f.: (x+x^2+2*x^3-x^4+x^5)/(1-x^2)^2. [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Feb 10 2009]
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EXAMPLE
| 0.546302489843790513255179465... = 0 + 1/(1 + 1/(1 + 1/(4 + 1/(1 + ...)))) [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jun 13 2009]
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PROG
| (PARI) { allocatemem(932245000); default(realprecision, 85000); x=contfrac(tan(1/2)); for (n=0, 20000, write("b019425.txt", n, " ", x[n+1])); } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jun 13 2009]
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CROSSREFS
| Cf. A161011 Decimal expansion. [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jun 13 2009]
Sequence in context: A040019 A019768 A158496 * A080102 A106475 A134829
Adjacent sequences: A019422 A019423 A019424 * A019426 A019427 A019428
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KEYWORD
| nonn,cofr
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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