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Search: id:A140109
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| A140109 |
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Quartets of prime x, composites y, z and S for Heron's formula. |
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+0
1
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| 7, 15, 20, 42, 7, 24, 25, 84, 13, 14, 15, 84, 13, 84, 85, 546, 17, 8, 15, 60, 17, 9, 10, 36, 29, 20, 21, 210, 37, 12, 35, 210, 41, 9, 40, 180, 53, 45, 48, 1080, 73, 48, 55, 1320, 89, 39, 80, 1560, 97, 65, 72, 2340, 101, 20, 99, 990, 109, 60, 91, 2730, 113, 15, 112, 840
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Heron's formula (x+y+z)*(x+y-z)*(x+z-y)*(y+z-x)/16=S^2
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EXAMPLE
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The quartets are: (7, 15, 20, 42), (7, 24, 25, 84), (13, 14, 15, 84), etc.
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CROSSREFS
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Cf. A140385, A140391, A140384.
Sequence in context: A154618 A138641 A115783 this_sequence A064397 A151971 A014659
Adjacent sequences: A140106 A140107 A140108 this_sequence A140110 A140111 A140112
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KEYWORD
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nonn
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jul 10 2008
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EXTENSIONS
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This should be replaced by four linked sequences! As it stands it is not a proper sequence. - N. J. A. Sloane (njas(AT)research.att.com), Jul 11 2008
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