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A001902
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Successive denominators of Wallis's approximation to pi/2 (reduced).
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7
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1, 3, 9, 45, 75, 175, 1225, 11025, 19845, 43659, 160083, 693693, 1288287, 2760615, 41409225, 703956825, 1329696225, 2807136475, 10667118605, 44801898141, 85530896451, 178837328943, 1371086188563, 11425718238025
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| H.-D. Ebbinghaus et al., Numbers, Springer, 1990, p. 146.
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LINKS
| J. Sondow, A faster product for Pi and a new integral for ln(Pi/2), Amer. Math. Monthly 112 (2005), 729-734 and 113 (2006), 670.
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FORMULA
| ... 2.2.4.4.6.6....2n.2n/1.3.3.5.5.7.7....(2n-1).(2n+1) ...
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CROSSREFS
| Numerators are A001901.
Sequence in context: A028858 A058106 A021103 * A192891 A068100 A012821
Adjacent sequences: A001899 A001900 A001901 * A001903 A001904 A001905
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KEYWORD
| nonn,frac
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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