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Search: id:A105199
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| A105199 |
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Decimal expansion of arctan(2). |
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+0
4
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| 1, 1, 0, 7, 1, 4, 8, 7, 1, 7, 7, 9, 4, 0, 9, 0, 5, 0, 3, 0, 1, 7, 0, 6, 5, 4, 6, 0, 1, 7, 8, 5, 3, 7, 0, 4, 0, 0, 7, 0, 0, 4, 7, 6, 4, 5, 4, 0, 1, 4, 3, 2, 6, 4, 6, 6, 7, 6, 5, 3, 9, 2, 0, 7, 4, 3, 3, 7, 1, 0, 3, 3, 8, 9, 7, 7, 3, 6, 2, 7, 9, 4, 0, 1, 3, 4, 1, 7, 1, 2, 8, 6, 8, 6, 1, 7, 0, 6, 4, 1, 4, 3, 4, 5, 4
(list; cons; graph; listen)
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OFFSET
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0,4
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COMMENT
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atan(2) + A073000 = pi/2
Contribution from Clark Kimberling (ck6(AT)evansville.edu), Feb 10 2009: (Start)
Arctan(2) is the (minimal) central angle of a regular icosahedron, which is
the platonic solid having 20 faces and 12 vertices. The (minimal) central
angle is AOB, where A and B are any neighboring pair of vertices and O is
the center. To evaluate AOB, it is helpful to start with 12 vertices:
(0,c*t,d), (d,0,c*t), (c*t,d,0) where c=(1 or -1) and d=(1 or -1) and t is
the golden ratio, (1+sqrt(5))/2. For neighboring vertices, one can select
(t,1,0) and (0,t,1). (End)
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EXAMPLE
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1.10714871779409050301706546017853704007004764540143264667653920743371033897736279401341712868617064143454...
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CROSSREFS
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Sequence in context: A021018 A010145 A073008 this_sequence A020791 A086210 A085467
Adjacent sequences: A105196 A105197 A105198 this_sequence A105200 A105201 A105202
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KEYWORD
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cons,nonn
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AUTHOR
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Bryan Jacobs (bryanjj(AT)gmail.com), Apr 12 2005
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