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A219529 Coordination sequence for 3.3.4.3.4 Archimedean tiling. 54
1, 5, 11, 16, 21, 27, 32, 37, 43, 48, 53, 59, 64, 69, 75, 80, 85, 91, 96, 101, 107, 112, 117, 123, 128, 133, 139, 144, 149, 155, 160, 165, 171, 176, 181, 187, 192, 197, 203, 208, 213, 219, 224, 229, 235, 240, 245, 251, 256, 261, 267, 272, 277, 283, 288, 293, 299 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n) is the number of vertices of the 3.3.4.3.4 tiling (which has three triangles and two squares, in the given cyclic order, meeting at each vertex) whose shortest path connecting them to a given origin vertex contains n edges.

First few terms provided by Allan C. Wechsler; Fred Lunnon and Fred Helenius gave the next few; Fred Lunnon suggested that the recurrence was a(n+3) = a(n) + 16 for n > 1. [This conjecture is true - see the CGS-NJAS link or a proof. - N. J. A. Sloane, Dec 31 2017]

Appears also to be coordination sequence for node of type V2 in "krd" 2-D tiling (or net). This should be easy to prove by the coloring book method (see link). - N. J. A. Sloane, Mar 25 2018

Appears also to be coordination sequence for node of type V1 in "krj" 2-D tiling (or net). This also should be easy to prove by the coloring book method (see link). - N. J. A. Sloane, Mar 26 2018

REFERENCES

Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Table 2.2.1, page 67, 1st row, 2nd tiling, also 2nd row, third tiling.

LINKS

Joseph Myers, Table of n, a(n) for n = 0..1000

Brian Galebach, Collection of n-Uniform Tilings. See Numbers 14 and 17 from the list of 20 2-uniform tilings.

Brian Galebach, k-uniform tilings (k <= 6) and their A-numbers

C. Goodman-Strauss and N. J. A. Sloane, A Coloring Book Approach to Finding Coordination Sequences, arXiv:1803.08530, March 2018.

Branko Grünbaum and Geoffrey C. Shephard, Tilings by regular polygons, Mathematics Magazine, 50 (1977), 227-247.

Kival Ngaokrajang, Illustration of initial terms

Reticular Chemistry Structure Resource, tts

Reticular Chemistry Structure Resource (RCSR), The krd tiling (or net)

Reticular Chemistry Structure Resource (RCSR), The krj tiling (or net)

N. J. A. Sloane, The uniform planar nets and their A-numbers [Annotated scanned figure from Gruenbaum and Shephard (1977)]

FORMULA

Conjectured to be a(n) = floor((16n+1)/3) for n>0; a(0) = 1; this is a consequence of the suggested recurrence due to Lunnon (see comments). [This conjecture is true - see the CGS-NJAS link in A296368 for a proof. - N. J. A. Sloane, Dec 31 2017]

G.f.: (x+1)^4/((x^2+x+1)*(x-1)^2). - N. J. A. Sloane, Feb 07 2018

PROG

(Haskell)

-- Very slow, could certainly be accelerated.  SST stands for Snub Square Tiling.

setUnion [] l2 = l2

setUnion (a:rst) l2 = if (elem a l2) then doRest else (a:doRest)

  where doRest = setUnion rst l2

setDifference [] l2 = []

setDifference (a:rst) l2 = if (elem a l2) then doRest else (a:doRest)

  where doRest = setDifference rst l2

adjust k = (if (even k) then 1 else -1)

weirdAdjacent (x, y) = (x+(adjust y), y+(adjust x))

sstAdjacents (x, y) = [(x+1, y), (x-1, y), (x, y+1), (x, y-1), (weirdAdjacent (x, y))]

sstNeighbors core = foldl setUnion core (map sstAdjacents core)

sstGlob n core = if (n == 0) then core else (sstGlob (n-1) (sstNeighbors core))

sstHalo core = setDifference (sstNeighbors core) core

origin = [(0, 0)]

a219529 n = length (sstHalo (sstGlob (n-1) origin))

-- Allan C. Wechsler, Nov 30 2012

CROSSREFS

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).

Coordination sequences for the 20 2-uniform tilings in the order in which they appear in the Galebach catalog, together with their names in the RCSR database (two sequences per tiling): #1 krt A265035, A265036; #2 cph A301287, A301289; #3 krm A301291, A301293; #4 krl A301298, A298024; #5 krq A301299, A301301; #6 krs A301674, A301676; #7 krr A301670, A301672; #8 krk A301291, A301293; #9 krn A301678, A301680; #10 krg A301682, A301684; #11 bew A008574, A296910; #12 krh A301686, A301688; #13 krf A301690, A301692; #14 krd A301694, A219529; #15 krc A301708, A301710; #16 usm A301712, A301714; #17 krj A219529, A301697; #18 kre A301716, A301718; #19 krb A301720, A301722; #20 kra A301724, A301726.

Cf. A301694, A301697.

Sequence in context: A314128 A314129 A314130 * A314131 A314132 A301726

Adjacent sequences:  A219526 A219527 A219528 * A219530 A219531 A219532

KEYWORD

easy,nonn

AUTHOR

Allan C. Wechsler, Nov 21 2012

EXTENSIONS

Corrected attributions and epistemological status in Comments; provided slow Haskell code - Allan C. Wechsler, Nov 30 2012

Extended by Joseph Myers, Dec 04 2014

STATUS

approved

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Last modified August 18 22:15 EDT 2018. Contains 313840 sequences. (Running on oeis4.)