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A195321 a(n) = 18*n^2. 10
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

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

LINKS

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).

FORMULA

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

MAPLE

A195321:=n->18*n^2; seq(A195321(n), n=0..50); # Wesley Ivan Hurt, Jun 19 2014

MATHEMATICA

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 *)

PROG

(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

CROSSREFS

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

KEYWORD

nonn,easy

AUTHOR

Omar E. Pol, Sep 16 2011

STATUS

approved

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Last modified February 5 03:17 EST 2023. Contains 360082 sequences. (Running on oeis4.)