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 A298029 Coordination sequence of Dual(3.4.6.4) tiling with respect to a trivalent node. 22
 1, 3, 6, 12, 18, 33, 39, 51, 57, 69, 75, 87, 93, 105, 111, 123, 129, 141, 147, 159, 165, 177, 183, 195, 201, 213, 219, 231, 237, 249, 255, 267, 273, 285, 291, 303, 309, 321, 327, 339, 345, 357, 363, 375, 381, 393, 399, 411, 417, 429, 435, 447, 453, 465, 471, 483, 489, 501, 507, 519, 525, 537, 543, 555 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Also known as the mta net. This is one of the Laves tilings. LINKS Colin Barker, Table of n, a(n) for n = 0..1000 C. Goodman-Strauss and N. J. A. Sloane, A Coloring Book Approach to Finding Coordination Sequences, Acta Cryst. A75 (2019), 121-134, also on NJAS's home page. Also arXiv:1803.08530. Reticular Chemistry Structure Resource (RCSR), The mta tiling (or net) N. J. A. Sloane, The Dual(3.4.6.4) tiling N. J. A. Sloane, Overview of coordination sequences of Laves tilings [Fig. 2.7.1 of Grünbaum-Shephard 1987 with A-numbers added and in some cases the name in the RCSR database] Wikipedia, Laves tilings Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA Theorem: For n >= 5, if n is even then a(n) = 9*n-15, otherwise a(n) = 9*n-12. The proof uses the "coloring book" method described in the Goodman-Strauss & Sloane article. - N. J. A. Sloane, Jan 24 2018 G.f.: -(3*x^7 - 9*x^5 - 3*x^4 - 4*x^3 - 2*x^2 - 2*x - 1)/((1 - x)*(1 - x^2)). a(n) = a(n-1) + a(n-2) - a(n-3) for n>5. - Colin Barker, Jan 25 2018 a(n) = (3/2)*(6*n - (-1)^n - 9) for n>4. - Bruno Berselli, Jan 25 2018 a(n) = 3*A007310(n-1), n>4. - R. J. Mathar, Jan 29 2018 MATHEMATICA Join[{1, 3, 6, 12, 18}, LinearRecurrence[{1, 1, -1}, {33, 39, 51}, 60]] (* Jean-François Alcover, Jan 07 2019 *) PROG (PARI) Vec((1 + 2*x + 2*x^2 + 4*x^3 + 3*x^4 + 9*x^5 - 3*x^7) / ((1 - x)^2*(1 + x)) + O(x^60)) \\ Colin Barker, Jan 25 2018 CROSSREFS Cf. A008574, A298030 (partial sums), A298031 (for a tetravalent node), A298033 (hexavalent node). List of coordination sequences for Laves tilings (or duals of uniform planar nets): [3,3,3,3,3.3] = A008486; [3.3.3.3.6] = A298014, A298015, A298016; [3.3.3.4.4] = A298022, A298024; [3.3.4.3.4] = A008574, A296368; [3.6.3.6] = A298026, A298028; [3.4.6.4] = A298029, A298031, A298033; [3.12.12] = A019557, A298035; [4.4.4.4] = A008574; [4.6.12] = A298036, A298038, A298040; [4.8.8] = A022144, A234275; [6.6.6] = A008458. Sequence in context: A006156 A171370 A061776 * A074899 A318872 A267591 Adjacent sequences:  A298026 A298027 A298028 * A298030 A298031 A298032 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jan 21 2018 STATUS approved

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Last modified March 18 22:11 EDT 2019. Contains 321305 sequences. (Running on oeis4.)