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Search: id:A143689
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| 1, 2, 6, 13, 23, 36, 52, 71, 93, 118, 146, 177, 211, 248
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Equals left border of triangle A033292
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FORMULA
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a(n) = A000326(n+1) - 3n. A000326 = pentagonal numbers. Equals binomial transform of [1, 1, 3, 0, 0, 0,...].
a(n) = (3n^2-n+2)/2 = A027599(n+1)/2. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 03 2008
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EXAMPLE
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a(4) = 23 = A000326(5) - 12 = (35 - 12).
a(4) = 23 = (1, 4, 6, 4, 1) dot (1, 1, 3, 0, 0) = (1 + 4 + 18 + 0 + 0).
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CROSSREFS
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Cf. A000326, A033292.
Adjacent sequences: A143686 A143687 A143688 this_sequence A143690 A143691 A143692
Sequence in context: A026052 A049616 A064960 this_sequence A011891 A003600 A000135
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KEYWORD
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nonn
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AUTHOR
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Gary W. Adamson (qntmpkt(AT)yahoo.com), Aug 29 2008
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EXTENSIONS
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Corrected index of A000326 in definition, formula and example. - R. J. Mathar, Sep 03 2008
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