cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A301716 Coordination sequence for node of type V1 in "kre" 2-D tiling (or net).

Original entry on oeis.org

1, 6, 12, 18, 18, 30, 36, 36, 48, 48, 54, 66, 66, 72, 78, 84, 90, 96, 102, 102, 114, 120, 120, 132, 132, 138, 150, 150, 156, 162, 168, 174, 180, 186, 186, 198, 204, 204, 216, 216, 222, 234, 234, 240, 246, 252, 258, 264, 270, 270, 282, 288, 288, 300, 300, 306
Offset: 0

Views

Author

N. J. A. Sloane, Mar 26 2018

Keywords

Comments

Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 30 2023

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, 3rd tiling.

Crossrefs

Cf. A301718.
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.

Programs

  • Mathematica
    LinearRecurrence[{0,0,1,0,1,0,0,-1},{1,6,12,18,18,30,36,36,48},100] (* Paolo Xausa, Nov 16 2023 *)
  • PARI
    See Links section.

Formula

G.f.: (x^8+6*x^7+12*x^6+17*x^5+12*x^4+17*x^3+12*x^2+6*x+1) / ((1-x^3)*(1-x^5)). - N. J. A. Sloane, Mar 28 2018

Extensions

More terms from Rémy Sigrist, Mar 28 2018

A301718 Coordination sequence for node of type V2 in "kre" 2-D tiling (or net).

Original entry on oeis.org

1, 5, 11, 17, 23, 28, 33, 39, 45, 51, 56, 61, 67, 73, 79, 84, 89, 95, 101, 107, 112, 117, 123, 129, 135, 140, 145, 151, 157, 163, 168, 173, 179, 185, 191, 196, 201, 207, 213, 219, 224, 229, 235, 241, 247, 252, 257, 263, 269, 275, 280, 285, 291, 297, 303, 308
Offset: 0

Views

Author

N. J. A. Sloane, Mar 26 2018

Keywords

Comments

Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 30 2023

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, 3rd tiling.

Crossrefs

Cf. A301716.
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.

Programs

  • Mathematica
    LinearRecurrence[{1,0,0,0,1,-1},{1,5,11,17,23,28,33},100] (* Paolo Xausa, Nov 16 2023 *)
  • PARI
    \\ See Links section.

Formula

G.f.: (x^4+2*x^3+x^2+2*x+1)*(x+1)^2 / ((1-x)*(1-x^5)). - N. J. A. Sloane, Mar 28 2018
Conjecture: a(n) ~ 28*n/5. - Stefano Spezia, Mar 29 2023

Extensions

More terms from Rémy Sigrist, Mar 28 2018

A301720 Coordination sequence for node of type V1 in "krb" 2-D tiling (or net).

Original entry on oeis.org

1, 6, 9, 18, 21, 24, 36, 36, 39, 54, 51, 54, 72, 66, 69, 90, 81, 84, 108, 96, 99, 126, 111, 114, 144, 126, 129, 162, 141, 144, 180, 156, 159, 198, 171, 174, 216, 186, 189, 234, 201, 204, 252, 216, 219, 270, 231, 234, 288, 246, 249, 306, 261, 264, 324, 276, 279, 342, 291, 294, 360, 306, 309, 378, 321
Offset: 0

Views

Author

N. J. A. Sloane, Mar 26 2018

Keywords

Comments

Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 30 2023

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Table 2.2.1, page 66, 1st row, 2nd tiling.

Crossrefs

Cf. A301722.
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.

Programs

  • Mathematica
    LinearRecurrence[{0,0,2,0,0,-1},{1,6,9,18,21,24,36},100] (* Paolo Xausa, Nov 16 2023 *)

Formula

G.f.: -(-x^6-6*x^5-9*x^4-16*x^3-9*x^2-6*x-1)/(x^6-2*x^3+1). - N. J. A. Sloane, Mar 29 2018

Extensions

a(11)-a(100) from Davide M. Proserpio, Mar 28 2018

A301722 Coordination sequence for node of type V2 in "krb" 2-D tiling (or net).

Original entry on oeis.org

1, 5, 10, 15, 22, 27, 31, 38, 43, 47, 54, 59, 63, 70, 75, 79, 86, 91, 95, 102, 107, 111, 118, 123, 127, 134, 139, 143, 150, 155, 159, 166, 171, 175, 182, 187, 191, 198, 203, 207, 214, 219, 223, 230, 235, 239, 246, 251, 255, 262, 267, 271, 278, 283, 287, 294, 299, 303, 310, 315, 319, 326, 331, 335
Offset: 0

Views

Author

N. J. A. Sloane, Mar 26 2018

Keywords

Comments

Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 30 2023

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Table 2.2.1, page 66, 1st row, 2nd tiling.

Crossrefs

Cf. A301720.
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.

Programs

  • Mathematica
    LinearRecurrence[{1,0,1,-1},{1,5,10,15,22,27,31},100] (* Paolo Xausa, Nov 16 2023 *)

Formula

G.f.: (-x^6+3*x^4+4*x^3+5*x^2+4*x-1)/(x^4-x^3-x+1). - Ray Chandler, Aug 30 2023

Extensions

a(11)-a(100) from Davide M. Proserpio, Mar 28 2018

A301724 Coordination sequence for node of type V1 in "kra" 2-D tiling (or net).

Original entry on oeis.org

1, 6, 10, 16, 23, 27, 31, 38, 44, 48, 54, 60, 64, 70, 77, 81, 85, 92, 98, 102, 108, 114, 118, 124, 131, 135, 139, 146, 152, 156, 162, 168, 172, 178, 185, 189, 193, 200, 206, 210, 216, 222, 226, 232, 239, 243, 247, 254, 260, 264, 270, 276, 280, 286, 293, 297, 301, 308, 314, 318, 324, 330, 334, 340
Offset: 0

Views

Author

N. J. A. Sloane, Mar 26 2018

Keywords

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Table 2.2.1, page 66, 1st row, 1st tiling.

Crossrefs

Cf. A301726.
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.

Programs

  • Mathematica
    CoefficientList[Series[(x^10+4x^9+6x^7+x^6+3x^5+x^4+6x^3+4x+1)/((x^4+x^3+x^2+x+1)(x^4-x^3+x^2-x+1)(x-1)^2),{x,0,100}],x] (* Harvey P. Dale, Aug 08 2021 *)

Formula

G.f.: (x^10+4*x^9+6*x^7+x^6+3*x^5+x^4+6*x^3+4*x+1)/((x^4+x^3+x^2+x+1)*(x^4-x^3+x^2-x+1)*(x-1)^2). - N. J. A. Sloane, Mar 29 2018

Extensions

a(11)-a(100) from Davide M. Proserpio, Mar 28 2018

A301726 Coordination sequence for node of type V2 in "kra" 2-D tiling (or net).

Original entry on oeis.org

1, 5, 11, 16, 21, 27, 33, 38, 43, 49, 54, 59, 65, 70, 75, 81, 87, 92, 97, 103, 108, 113, 119, 124, 129, 135, 141, 146, 151, 157, 162, 167, 173, 178, 183, 189, 195, 200, 205, 211, 216, 221, 227, 232, 237, 243, 249, 254, 259, 265, 270, 275, 281, 286, 291, 297, 303, 308, 313, 319, 324, 329, 335, 340
Offset: 0

Views

Author

N. J. A. Sloane, Mar 26 2018

Keywords

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Table 2.2.1, page 66, 1st row, 1st tiling.

Crossrefs

Cf. A301724.
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.

Programs

  • Mathematica
    CoefficientList[Series[(x^2+x+1)(x^8+2x^7+3x^4+2x+1)/((x^4+x^3+x^2+x+1)(x^4-x^3+x^2-x+1)(x-1)^2),{x,0,110}],x] (* Harvey P. Dale, Sep 25 2020 *)

Formula

G.f. = (x^2+x+1)*(x^8+2*x^7+3*x^4+2*x+1)/((x^4+x^3+x^2+x+1)*(x^4-x^3+x^2-x+1)*(x-1)^2). - N. J. A. Sloane, Mar 29 2018

Extensions

a(11)-a(100) from Davide M. Proserpio, Mar 28 2018

A265035 Coordination sequence of 2-uniform tiling {3.4.6.4, 4.6.12} with respect to a point of type 4.6.12.

Original entry on oeis.org

1, 3, 6, 9, 11, 14, 17, 21, 25, 28, 30, 32, 35, 39, 43, 46, 48, 50, 53, 57, 61, 64, 66, 68, 71, 75, 79, 82, 84, 86, 89, 93, 97, 100, 102, 104, 107, 111, 115, 118, 120, 122, 125, 129, 133, 136, 138, 140, 143, 147, 151, 154, 156, 158, 161, 165, 169, 172, 174, 176
Offset: 0

Views

Author

N. J. A. Sloane, Dec 12 2015

Keywords

Comments

Joseph Myers (Dec 14 2015) reports that "My program for coordination sequences requires describing the tiling structure under translation, listing all edges in the form: (class1, 0, 0) has an edge to (class2, x, y). The present tiling has 18 orbits of vertices under translation and 30 orbits of edges under translation (each of which is described in both directions). So in principle it could generate the other 19 2-uniform tilings, but without a cross check with hand-computed terms there's a risk of e.g. missing some edges, and a fair amount of work producing all the descriptions of translation classes of edges."
Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 31 2023

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See page 67, 4th row, 3rd tiling.
  • Otto Krötenheerdt, Die homogenen Mosaike n-ter Ordnung in der euklidischen Ebene, I, II, III, Wiss. Z. Martin-Luther-Univ. Halle-Wittenberg, Math-Natur. Reihe, 18 (1969), 273-290; 19 (1970), 19-38 and 97-122. [Includes classification of 2-uniform tilings]
  • Anton Shutov and Andrey Maleev, Coordination sequences of 2-uniform graphs, Z. Kristallogr., 235 (2020), 157-166.

Crossrefs

See A265036 for the other type of point.
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.

Programs

  • Mathematica
    LinearRecurrence[{3,-4,3,-1},{1,3,6,9,11,14,17,21,25},100] (* Paolo Xausa, Nov 15 2023 *)

Formula

Based on the b-file, the g.f. appears to be (1+x^2+2*x^5-2*x^6+2*x^7-x^8)/(1-3*x+4*x^2-3*x^3+x^4). This matches the first 1000 terms, so is probably correct. - N. J. A. Sloane, Dec 14 2015
Conjectured g.f. is equivalent to a(n) = 3*n - A010892(n+1) for n >= 5. - R. J. Mathar, Oct 09 2020

Extensions

Extended by Joseph Myers, Dec 13 2015
b-file extended by Joseph Myers, Dec 18 2015

A008579 Coordination sequence for planar net 3.6.3.6. Spherical growth function for a certain reflection group in plane.

Original entry on oeis.org

1, 4, 8, 14, 18, 22, 28, 30, 38, 38, 48, 46, 58, 54, 68, 62, 78, 70, 88, 78, 98, 86, 108, 94, 118, 102, 128, 110, 138, 118, 148, 126, 158, 134, 168, 142, 178, 150, 188, 158, 198, 166, 208, 174, 218, 182, 228, 190, 238, 198, 248, 206, 258, 214, 268, 222, 278
Offset: 0

Views

Author

Keywords

Comments

Interesting because coefficients never become monotonic.
Also the coordination sequence for a planar net made of densely packed circles. - Yuriy Sibirmovsky, Sep 11 2016
Described by J.-G. Eon (2014) as the coordination sequence of the Kagome net. - N. J. A. Sloane, Jan 03 2018

References

  • P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 161 (but beware errors).

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).

Programs

  • Haskell
    a008579 0 = 1
    a008579 1 = 4
    a008579 n = (10 - 2*m) * n' + 8*m - 2 where (n',m) = divMod n 2
    a008579_list = 1 : 4 : concatMap (\x -> map (* 2) [5*x-1,4*x+3]) [1..]
    -- Reinhard Zumkeller, Nov 12 2012
  • Maple
    f := n->if n mod 2 = 0 then 10*(n/2)-2 else 8*(n-1)/2+6 fi;
  • Mathematica
    a[n_?EvenQ] := 10*n/2-2; a[n_?OddQ] := 8*(n-1)/2+6; a[0] = 1; a[1] = 4; Table[a[n], {n, 0, 45}] (* Jean-François Alcover, Nov 18 2011, after Maple *)
    CoefficientList[Series[(1+2x)(1+2x+2x^2+2x^3-x^4)/(1-x^2)^2,{x,0,50}],x] (* or *) LinearRecurrence[{0,2,0,-1},{1,4,8,14,18,22},50] (* Harvey P. Dale, Sep 05 2018 *)

Formula

G.f.: (1 + 2*x)*(1 + 2*x + 2*x^2 + 2*x^3 - x^4)/(1 - x^2)^2.
From R. J. Mathar, Nov 26 2014: (Start)
a(2n) = A017365(n), n > 0.
a(2n+1) = A017137(n), n > 0. (End)
From Stefano Spezia, Aug 07 2022: (Start)
a(n) = (9 + (-1)^n)*n/2 - 2*(-1)^n for n > 1.
E.g.f.: 3 - 2*x + (4*x - 2)*cosh(x) + (5*x + 2)*sinh(x). (End)

A250122 Coordination sequence for planar net 3.12.12.

Original entry on oeis.org

1, 3, 4, 6, 8, 12, 14, 15, 18, 21, 22, 24, 28, 30, 30, 33, 38, 39, 38, 42, 48, 48, 46, 51, 58, 57, 54, 60, 68, 66, 62, 69, 78, 75, 70, 78, 88, 84, 78, 87, 98, 93, 86, 96, 108, 102, 94, 105, 118, 111, 102, 114, 128, 120, 110, 123, 138, 129
Offset: 0

Views

Author

Darrah Chavey, Nov 23 2014

Keywords

Comments

Also, growth series for group with presentation < S, T : S^2 = T^3 = (S*T)^6 = 1 >. See Magma program in A298805. - N. J. A. Sloane, Feb 06 2018

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).
Cf. A298805.

Programs

  • Mathematica
    Join[{1, 3, 4}, LinearRecurrence[{2, -3, 4, -3, 2, -1}, {6, 8, 12, 14, 15, 18}, 100]] (* Jean-François Alcover, Aug 05 2018 *)

Formula

From Joseph Myers, Nov 28 2014: (Start)
Empirically,
a(4n) = 10n - 2 except for a(0) = 1
a(4n+1) = 9n + 3
a(4n+2) = 8n + 6 except for a(2) = 4
a(4n+3) = 9n + 6. (End)
If these are correct, the sequence has g.f.
-(-1 - x - x^2 - 3*x^3 + x^4 - 5*x^5 + 3*x^6 - 4*x^7 + 2*x^8)/((x - 1)^2*(x^2 + 1)^2). - N. J. A. Sloane, Nov 28 2014
All the above conjectures are true. - N. J. A. Sloane, Dec 31 2015
E.g.f.: (9*x*cosh(x) - 4*(2*cos(x) + x^2 - 3) + 9*x*sinh(x) - (x - 3)*sin(x))/4. - Stefano Spezia, Jan 05 2023

Extensions

a(8) onwards from Maurizio Paolini and Joseph Myers (independently), Nov 28 2014

A072154 Coordination sequence for the planar net 4.6.12.

Original entry on oeis.org

1, 3, 5, 7, 9, 12, 15, 17, 19, 21, 24, 27, 29, 31, 33, 36, 39, 41, 43, 45, 48, 51, 53, 55, 57, 60, 63, 65, 67, 69, 72, 75, 77, 79, 81, 84, 87, 89, 91, 93, 96, 99, 101, 103, 105, 108, 111, 113, 115, 117, 120, 123, 125, 127, 129, 132, 135, 137
Offset: 0

Views

Author

N. J. A. Sloane, Jun 28 2002

Keywords

Comments

There is only one type of node in this structure: each node meets a square, a hexagon and a 12-gon.
The coordination sequence with respect to a particular node gives the number of nodes that can be reached from that node in n steps along edges.
Also, coordination sequence for the aluminophosphate AlPO_4-5 structure.

References

  • A. V. Shutov, On the number of words of a given length in plane crystallographic groups (Russian), Zap. Nauchn. Sem. S.-Peterburg. Otdel. Mat. Inst. Steklov. (POMI) 302 (2003), Anal. Teor. Chisel i Teor. Funkts. 19, 188--197, 203; translation in J. Math. Sci. (N.Y.) 129 (2005), no. 3, 3922-3926 [MR2023041]. See Table 1, line "p6m" (but beware typos).

Crossrefs

For partial sums see A265078.
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).
See also A301730.

Programs

  • Mathematica
    Join[{1}, LinearRecurrence[{1, 0, 0, 0, 1, -1}, {3, 5, 7, 9, 12, 15}, 100]] (* Jean-François Alcover, Dec 13 2018 *)

Formula

Empirical g.f.: (x+1)^2*(x^2-x+1)*(x^2+x+1)/((x-1)^2*(x^4+x^3+x^2+x+1)). - Colin Barker, Nov 18 2012
This empirical g.f. can also be written as (1 + 2*x + 2*x^2 + 2*x^3 + 2*x^4 + 2*x^5 + x^6)/(1 - x - x^5 + x^6). - N. J. A. Sloane, Dec 20 2015
Theorem: For n >= 7, a(n) = a(n-1) + a(n-5) - a(n-6), and a(5k) = 12k (k > 0), a(5k+m) = 12k + 2m + 1 (k >= 0, 1 <= m < 5). This also implies the conjectured g.f.'s. - N. J. A. Sloane, conjectured Dec 20 2015, proved Jan 20 2018.
Notes on the proof, from N. J. A. Sloane, Jan 20 2018 (Start)
The proof uses the "coloring book" method described in the Goodman-Strauss & Sloane article. The subgraph H is shown above in the links.
The figure is divided into 6 sectors by the blue trunks. In the interior of each sector, working outwards from the base point P at the origin, there are successively 1,2,3,4,... (red) 12-gons. All the 12-gons (both red and blue) have a unique closest point to P.
If the closest point in a 12-gon is at distance d from P, then the contributions of the 12 points of the 12-gon to a(d), a(d+1), ..., a(d+6) are 1,2,2,2,2,2,1, respectively.
The rest of the proof is now a matter of simple counting.
The blue 12-gons (along the trunks) are especially easy to count, because there is a unique blue 12-gon at shortest distance d from P for d = 1,2,3,4,...
(End)
a(n) = 2*(6*n + sqrt(1 + 2/sqrt(5))*sin(2*n*Pi/5) + sqrt(1 - 2/sqrt(5))*sin(4*n*Pi/5))/5 for n > 0. - Stefano Spezia, Jan 05 2023

Extensions

More terms from Sean A. Irvine, Sep 29 2011
Thanks to Darrah Chavey for pointing out that this is the planar net 4.6.12. - N. J. A. Sloane, Nov 24 2014
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