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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, 288, 331, 377, 426, 478, 533, 591, 652, 716, 783, 853, 926, 1002, 1081, 1163, 1248, 1336, 1427, 1521, 1618, 1718, 1821, 1927, 2036, 2148, 2263, 2381, 2502, 2626, 2753, 2883, 3016, 3152, 3291
(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
a(n)=3*n+a(n-1)-5 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 09 2009]
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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).
For n=2, a(2)=3*2+1-5=2; n=3, a(3)=3*3+2-5=6; n=4, a(4)=3*4+6-5=13 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 09 2009]
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CROSSREFS
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Cf. A000326, A033292.
Sequence in context: A026052 A049616 A064960 this_sequence A011891 A003600 A000135
Adjacent sequences: A143686 A143687 A143688 this_sequence A143690 A143691 A143692
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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
More terms a(15)-a(48)from Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 09 2009
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