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Search: id:A141631
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| 2, 7, 18, 35, 58, 87, 122, 163, 210, 263, 322, 387, 458, 535, 618, 707, 802, 903, 1010, 1123, 1242, 1367, 1498, 1635, 1778, 1927, 2082, 2243, 2410, 2583, 2762, 2947, 3138, 3335, 3538, 3747, 3962, 4183, 4410, 4643, 4882, 5127, 5378, 5635, 5898, 6167, 6442
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OFFSET
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1,1
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FORMULA
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a(n) = A133146(2n-2) = (n-2)^2+(n-1)(n+1)+n^2 = 3n^2-4n+3.
First differences: a(n+1)-a(n) = A016969(n-1). Second differences are A010722, third differences are A000004.
G.f.: x(2+x+3x^2)/(1-x)^3. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 15 2008
a(n)=6*n+a(n-1)-7 (with a(1)=2) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 11 2009]
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EXAMPLE
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For n=2, a(2)=6*2+2-7=7; n=3, a(3)=6*3+7-7=18; n=4, a(4)=6*4+18-7=35 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 11 2009]
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MATHEMATICA
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s=2; lst={s}; Do[s+=n+5; AppendTo[lst, s], {n, 0, 6!, 6}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 04 2008]
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CROSSREFS
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Sequence in context: A001114 A107615 A136583 this_sequence A077131 A086741 A051743
Adjacent sequences: A141628 A141629 A141630 this_sequence A141632 A141633 A141634
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KEYWORD
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nonn,less,new
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AUTHOR
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Paul Curtz (bpcrtz(AT)free.fr), Aug 28 2008
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EXTENSIONS
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Edited and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 15 2008
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