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A195321
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a(n) = 18*n^2.
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10
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0, 18, 72, 162, 288, 450, 648, 882, 1152, 1458, 1800, 2178, 2592, 3042, 3528, 4050, 4608, 5202, 5832, 6498, 7200, 7938, 8712, 9522, 10368, 11250, 12168, 13122, 14112, 15138, 16200, 17298, 18432, 19602, 20808, 22050, 23328, 24642, 25992, 27378, 28800
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OFFSET
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0,2
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COMMENTS
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Sequence found by reading the line from 0, in the direction 0, 18,..., in the square spiral whose vertices are the generalized hendecagonal numbers A195160. Semi-axis opposite to A195316 in the same spiral.
Area of a square with diagonal 6n. - Wesley Ivan Hurt, Jun 19 2014
Number of identical tessellation tiles that are composed of 48 equilateral edge joined triangles that can be formed into a order n hexagon. The example tiles shown in the link below are tessellated with eight sphinx tiles. See A291582. - Craig Knecht, Sep 02 2017
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Craig Knecht, Hexagon tessellation
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
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a(n) = 18*A000290(n) = 9*A001105(n) = 6*A033428(n) = 3*A033581(n) = 2*A016766(n).
G.f.: 18*x*(1+x)/(1-x)^3. - Wesley Ivan Hurt, Jun 20 2014
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MAPLE
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A195321:=n->18*n^2; seq(A195321(n), n=0..50); # Wesley Ivan Hurt, Jun 19 2014
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MATHEMATICA
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18 Range[0, 50]^2 (* or *) CoefficientList[Series[18 x*(1 + x)/(1 - x)^3, {x, 0, 30}], x] (* Wesley Ivan Hurt, Jun 20 2014 *)
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PROG
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(Magma)[18*n^2:n in [0..40]]; // Vincenzo Librandi, Sep 20 2011
(PARI) a(n)=18*n^2 \\ Charles R Greathouse IV, Jun 17 2017
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CROSSREFS
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Bisection of A195147.
Cf. A033581, A139098, A033583, A135453, A144555, A016802, A195322, A195323.
Sequence in context: A231328 A274577 A347360 * A069058 A262000 A007276
Adjacent sequences: A195318 A195319 A195320 * A195322 A195323 A195324
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KEYWORD
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nonn,easy
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AUTHOR
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Omar E. Pol, Sep 16 2011
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STATUS
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approved
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