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Search: id:A159919
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| A159919 |
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A square array of numbers, read by antidiagonals, called Sundaram's sieve |
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+0
2
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| 4, 7, 7, 10, 12, 10, 13, 17, 17, 13, 16, 22, 24, 22, 16, 19, 27, 31, 31, 27, 19, 22, 32, 38, 40, 38, 32, 22, 25, 37, 45, 49, 49, 45, 37, 25, 28, 42, 52, 58, 60, 58, 52, 42, 28, 31, 47, 59, 67, 71, 71, 67, 59, 47, 31, 34, 52, 66, 76, 82, 84, 82, 76, 66, 52, 34
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The sieve of Sundaram contains every number n > 3 for which the number 2n + 1
is composite. For any n absent from this array, 2n + 1 is either even or prime.
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REFERENCES
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Honsberger, Ross (1970). Ingenuity in Mathematics. New Mathematical Library #23. Mathematical Association of America. pp. 75. ISBN 0394709233.
Ogilvy, C. Stanley and John T. Anderson. Excursions in Number Theory. Oxford University Press, Inc., New York. A1966
New Zealand Maths Newletter 18 (October 2002). [On-line] www.nzmaths.co.nz/HelpCentre/Newsletter18.pdf September 8, 2004.
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LINKS
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Andrew Baxter, Sundaram's Sieve
Wikipedia, Sundaram's Sieve
Sundaram's Sieve
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FORMULA
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For row j/column k, the term T[j,k] = 2jk+j+k
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EXAMPLE
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For row 3/column 3, the term T[3,3] = 2*3*3+3+3 = 24
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CROSSREFS
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Sequence in context: A157298 A070326 A103711 this_sequence A131432 A088744 A061891
Adjacent sequences: A159916 A159917 A159918 this_sequence A159920 A159921 A159922
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KEYWORD
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easy,nonn
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AUTHOR
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Russell Walsmith (ixitol(AT)gmail.com), Apr 25 2009
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EXTENSIONS
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More terms from Philippe DELEHAM (kolotoko(AT)wanadoo.fr), May 11 2009
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