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 A296368 Coordination sequence for the Cairo or dual-3.3.4.3.4 tiling with respect to a trivalent point. 24
 1, 3, 8, 12, 15, 20, 25, 28, 31, 36, 41, 44, 47, 52, 57, 60, 63, 68, 73, 76, 79, 84, 89, 92, 95, 100, 105, 108, 111, 116, 121, 124, 127, 132, 137, 140, 143, 148, 153, 156, 159, 164, 169, 172, 175, 180, 185, 188, 191, 196, 201, 204, 207, 212, 217, 220, 223, 228 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS There are two types of point in this tiling. This is the coordination sequence with respect to a point of degree 3. The coordination sequence with respect to a point of degree 4 (see second illustration) is simply 1, 4, 8, 12, 16, 20, ..., the same as the coordination sequence for the 4.4.4.4 square grid (A008574). See the CGS-NJAS link for the proof. REFERENCES Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Fig. 9.1.3, drawing P_5-24, page 480. LINKS Rémy Sigrist, Table of n, a(n) for n = 0..1000 C. Goodman-Strauss and N. J. A. Sloane, A portion of the Cairo tiling C. Goodman-Strauss and N. J. A. Sloane, A Coloring Book Approach to Finding Coordination Sequences, arXiv:1803.08530, March 2018. Reticular Chemistry Structure Resource (RCSR), The mcm tiling (or net) Rémy Sigrist, PARI program for A296368 N. J. A. Sloane, Illustration of initial terms (for a trivalent point) N. J. A. Sloane, A tiling by rectangles which has the same graph and coordination sequences as the Cairo tiling (Seen on the streets of Piscataway, New Jersey, USA) 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] FORMULA The simplest formula is: a(0)=1, a(1)=2, a(2)=8, and thereafter a(n) = 4n if n is odd, 4n - 1 if n == 0 (mod 4), and 4n+1 if n == 2 (mod 4). (See the CGS-NJAS link for proof. - N. J. A. Sloane, May 10 2018) a(n + 4) = a(n) + 16 for any n >= 3. - Rémy Sigrist, Dec 23 2017 (See the CGS-NJAS link for a proof. - N. J. A. Sloane, Dec 30 2017) G.f.: -(x^6-x^5-2*x^4-4*x^2-x-1)/((x^2+1)*(x-1)^2). From Colin Barker, Dec 23 2017: (Start) a(n) = (8*n - (-i)^n - i^n) / 2 for n>2, where i=sqrt(-1). a(n) = 2*a(n-1) - 2*a(n-2) + 2*a(n-3) - a(n-4) for n>6. (End) MATHEMATICA Join[{1, 3, 8}, LinearRecurrence[{2, -2, 2, -1}, {12, 15, 20, 25}, 100]] (* Jean-François Alcover, Aug 05 2018 *) PROG (PARI) See Links section. CROSSREFS For partial sums see A296909. List of coordination sequences for uniform planar nets: A008458 (the planar net 3.3.3.3.3.3), A008486 (6^3), A008574 (4.4.4.4 and 3.4.6.4), A008576 (4.8.8), A008579 (3.6.3.6), A008706 (3.3.3.4.4), A072154 (4.6.12), A219529 (3.3.4.3.4), A250120 (3.3.3.3.6), A250122 (3.12.12). 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: A255199 A280239 A310284 * A183991 A022806 A084162 Adjacent sequences:  A296365 A296366 A296367 * A296369 A296370 A296371 KEYWORD nonn AUTHOR N. J. A. Sloane, Dec 21 2017 EXTENSIONS Terms a(8)-a(20) and RCSR link from Davide M. Proserpio, Dec 22 2017 More terms from Rémy Sigrist, Dec 23 2017 STATUS approved

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Last modified January 19 16:32 EST 2019. Contains 319309 sequences. (Running on oeis4.)