

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
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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 CGSNJAS link or a proof.  N. J. A. Sloane, Dec 31 2017]
Appears also to be coordination sequence for node of type V2 in "krd" 2D 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" 2D 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
Branko Grünbaum and Geoffrey C. Shephard, Tilings by regular polygons, Mathematics Magazine, 50 (1977), 227247.
Brian Galebach, Collection of nUniform Tilings. See Numbers 14 and 17 from the list of 20 2uniform tilings.
C. GoodmanStrauss and N. J. A. Sloane, A Coloring Book Approach to Finding Coordination Sequences, arXiv:1803.08530, March 2018.
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 Anumbers [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 CGSNJAS link in A296368 for a proof.  N. J. A. Sloane, Dec 31 2017]
G.f.: (x+1)^4/((x^2+x+1)*(x1)^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), (x1, y), (x, y+1), (x, y1), (weirdAdjacent (x, y))]
sstNeighbors core = foldl setUnion core (map sstAdjacents core)
sstGlob n core = if (n == 0) then core else (sstGlob (n1) (sstNeighbors core))
sstHalo core = setDifference (sstNeighbors core) core
origin = [(0, 0)]
a219529 n = length (sstHalo (sstGlob (n1) 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 2uniform 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, A361684; #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: A259067 A072557 A183989 * A301726 A278397 A172327
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



