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 A308321 Decimal expansion of 2^(-9/4); exact width of the A4 paper size measured in meters according to the ISO 216 standard. 1
 2, 1, 0, 2, 2, 4, 1, 0, 3, 8, 1, 3, 4, 2, 8, 6, 3, 5, 7, 5, 7, 7, 8, 1, 3, 6, 9, 0, 5, 8, 3, 0, 3, 7, 2, 3, 7, 6, 0, 0, 0, 8, 5, 6, 5, 5, 8, 9, 1, 9, 6, 1, 2, 7, 7, 0, 3, 3, 0, 6, 5, 2, 1, 4, 9, 3, 7, 3, 1, 1, 8, 8, 7, 3, 8, 4, 7, 5, 5, 5, 9, 9, 5, 3, 5, 8, 1, 0 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Also exact length of the A5 paper size measured in meters. According to the ISO 216 standard, the A0 paper size is defined to have an area of 1 square meter where the ratio of the length to the width is sqrt(2), so the length is 2^(1/4) m and the width is 2^(-1/4) m. For each n >= 0, the length of the size A(n+1) is equal to the width of the size A(n) and the width of the size A(n+1) is equal to half of the length of the size A(n), so the area of the size A(n+1) is half of that of A(n). Equivalently, the length of the A(n) size is 2^(-n/2 + 1/4) m and the width is 2^(-n/2 - 1/4) m. For the A4 size, the exact length and width are 2^(-7/4) m = 297.3 mm (A308320) and 2^(-9/4) m = 210.2 mm, and the actual length and width are 297 mm and 210 mm. LINKS Prepressure, A4 Wikipedia, ISO 216 EXAMPLE The exact lengths, widths and areas of the A-series is given by:   size |       exact length      |        exact width      | exact area (mm^2)    A0  | 2^(  1/4) m = 1189.2 mm | 2^(- 1/4) m =  840.8 mm |  1000000    A1  | 2^(- 1/4) m =  840.8 mm | 2^(- 3/4) m =  594.6 mm |   500000    A2  | 2^(- 3/4) m =  594.6 mm | 2^(- 5/4) m =  420.4 mm |   250000    A3  | 2^(- 5/4) m =  420.4 mm | 2^(- 7/4) m =  297.3 mm |   125000    A4  | 2^(- 7/4) m =  297.3 mm | 2^(- 9/4) m =  210.2 mm |    62500    A5  | 2^(- 9/4) m =  210.2 mm | 2^(-11/4) m =  148.7 mm |    31250    A6  | 2^(-11/4) m =  148.7 mm | 2^(-13/4) m =  105.1 mm |    15625    A7  | 2^(-13/4) m =  105.1 mm | 2^(-15/4) m =   74.3 mm |     7812.5    A8  | 2^(-15/4) m =   74.3 mm | 2^(-17/4) m =   52.6 mm |     3906.25    A9  | 2^(-17/4) m =   52.6 mm | 2^(-19/4) m =   37.2 mm |     1953.125    A10 | 2^(-19/4) m =   37.2 mm | 2^(-21/4) m =   26.3 mm |      976.5625 And the actual lengths, widths and areas is given by (note that the actual areas are always smaller than the exact areas):   size | actual length (mm) | actual width (mm) | actual area (mm^2)    A0  |        1189        |        841        |  999949 (99.9949%)    A1  |         841        |        594        |  499554 (99.9108%)    A2  |         594        |        420        |  249480 (99.7920%)    A3  |         420        |        297        |  124740 (99.7920%)    A4  |         297        |        210        |   62370 (99.7920%)    A5  |         210        |        148        |   31080 (99.4560%)    A6  |         148        |        105        |   15540 (99.4560%)    A7  |         105        |         74        |    7770 (99.4560%)    A8  |          74        |         52        |    3848 (98.5088%)    A9  |          52        |         37        |    1924 (98.5088%)    A10 |          37        |         26        |     962 (98.5088%) PROG (PARI) default(realprecision, 100); 2^(-9/4) CROSSREFS Cf. A010767 (2^(1/4)), A228497 (2^(-1/4)), A308320 (2^(-7/4)). Sequence in context: A128095 A316658 A189962 * A097854 A161515 A145580 Adjacent sequences:  A308318 A308319 A308320 * A308322 A308323 A308324 KEYWORD nonn,cons AUTHOR Jianing Song, May 20 2019 STATUS approved

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Last modified February 18 04:48 EST 2020. Contains 332011 sequences. (Running on oeis4.)