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 A308320 Decimal expansion of 2^(-7/4); exact length of the A4 paper size measured in meters according to the ISO 216 standard. 1
 2, 9, 7, 3, 0, 1, 7, 7, 8, 7, 5, 0, 6, 8, 0, 2, 6, 6, 6, 7, 9, 3, 7, 4, 9, 9, 2, 6, 4, 0, 1, 1, 8, 9, 7, 8, 8, 2, 3, 2, 4, 3, 0, 2, 3, 1, 1, 5, 9, 5, 4, 3, 5, 3, 2, 5, 4, 7, 5, 0, 5, 5, 6, 1, 7, 9, 8, 6, 6, 6, 6, 7, 0, 5, 6, 7, 2, 9, 2, 8, 9, 9, 6, 7, 6, 9, 5, 3 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Also exact width of the A3 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 and 2^(-9/4) m = 210.2 mm (A308321), 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^(-7/4) CROSSREFS Cf. A010767 (2^(1/4)), A228497 (2^(-1/4)), A308321 (2^(-9/4)). Sequence in context: A094044 A011070 A230480 * A254140 A200991 A013500 Adjacent sequences:  A308317 A308318 A308319 * A308321 A308322 A308323 KEYWORD nonn,cons AUTHOR Jianing Song, May 20 2019 STATUS approved

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Last modified February 17 21:46 EST 2020. Contains 332006 sequences. (Running on oeis4.)