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.

Showing 1-10 of 87 results. Next

A046106 G.f.: g.f. for A001411 / g.f. for A004018.

Original entry on oeis.org

1, 0, 8, 4, 48, 68, 284, 684, 1816, 5608, 12684, 42068, 92916, 304100, 688988, 2170020, 5088784, 15436172, 37281880, 109786204, 271062388, 781016892, 1958863988, 5555714820, 14090644980, 39503105472, 101000072900, 280693435596
Offset: 0

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Author

N. J. A. Sloane, based on a suggestion of Maurice Craig (Maurice.D.Craig(AT)BHPBilliton.com), May 11 2003

Keywords

Examples

			1 + 4*q + 12*q^2 + 36*q^3 + 100*q^4 + 284*q^5 + 780*q^6 + 2172*q^7 + 5916*q^8 + 16268*q^9 + ... / 1 + 4*q + 4*q^2 + 4*q^4 + 8*q^5 + 4*q^8 + 4*q^9 + ... = 1 + 8*q^2 + 4*q^3 + 48*q^4 + 68*q^5 + 284*q^6 + 684*q^7 + 1816*q^8 + 5608*q^9 + ...
		

Crossrefs

A001412 Number of n-step self-avoiding walks on cubic lattice.

Original entry on oeis.org

1, 6, 30, 150, 726, 3534, 16926, 81390, 387966, 1853886, 8809878, 41934150, 198842742, 943974510, 4468911678, 21175146054, 100121875974, 473730252102, 2237723684094, 10576033219614, 49917327838734, 235710090502158, 1111781983442406, 5245988215191414, 24730180885580790, 116618841700433358, 549493796867100942, 2589874864863200574, 12198184788179866902, 57466913094951837030, 270569905525454674614
Offset: 0

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Author

Keywords

References

  • Steven R. Finch, Mathematical Constants, Cambridge, 2003, section 5.10, pp. 331-339.
  • B. D. Hughes, Random Walks and Random Environments, Oxford 1995, vol. 1, p. 462.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Mathematica
    mo = {{1, 0, 0}, {-1, 0, 0}, {0, 1, 0}, {0, -1, 0}, {0, 0, 1}, {0, 0, -1}}; a[0] = 1;
    a[tg_, p_: {{0, 0, 0}}] := Block[{e, mv = Complement[Last[p] + # & /@ mo, p]},
    If[tg == 1, Return[Length@mv],Sum[a[tg - 1, Append[p, e]], {e, mv}]]];
    a /@ Range[0, 8]
    (* Robert FERREOL, Nov 30 2018, after the program of Giovanni Resta in A001411 *)
  • Python
    def add(L,x):
        M=[y for y in L];M.append(x)
        return(M)
    plus=lambda L,M : [x+y for x,y in zip(L,M)]
    mo=[[1,0,0],[-1,0,0],[0,1,0],[0,-1,0],[0,0,1],[0,0,-1]]
    def a(n,P=[[0,0,0]]):
        if n==0: return(1)
        mv1 = [plus(P[-1],x) for x in mo]
        mv2=[x for x in mv1 if x not in P]
        if n==1: return(len(mv2))
        else: return(sum(a(n-1,add(P,x)) for x in mv2))
    [a(n) for n in range(8)]
    # Robert FERREOL, Nov 30 2018

A001334 Number of n-step self-avoiding walks on hexagonal [ =triangular ] lattice.

Original entry on oeis.org

1, 6, 30, 138, 618, 2730, 11946, 51882, 224130, 964134, 4133166, 17668938, 75355206, 320734686, 1362791250, 5781765582, 24497330322, 103673967882, 438296739594, 1851231376374, 7812439620678, 32944292555934, 138825972053046
Offset: 0

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Keywords

Comments

The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.

References

  • A. J. Guttmann, Asymptotic analysis of power-series expansions, pp. 1-234 of C. Domb and J. L. Lebowitz, editors, Phase Transitions and Critical Phenomena. Vol. 13, Academic Press, NY, 1989.
  • B. D. Hughes, Random Walks and Random Environments, Oxford 1995, vol. 1, p. 459.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Mathematica
    mo={{2, 0},{-1, 1},{-1, -1},{-2, 0},{1, -1},{1, 1}}; a[0]=1;
    a[tg_, p_:{{0, 0}}] := Block[{e, mv = Complement[Last[p]+# & /@ mo, p]}, If[tg == 1, Length@mv, Sum[a[tg-1, Append[p, e]], {e, mv}]]];
    a /@ Range[0, 6]
    (* Robert FERREOL, Nov 28 2018; after the program of Giovanni Resta in A001411 *)
  • Python
    def add(L,x):
        M=[y for y in L];M.append(x)
        return(M)
    plus=lambda L,M : [x+y for x,y in zip(L,M)]
    mo=[[2,0],[-1,1],[-1, -1],[-2,0],[1,-1],[1, 1]]
    def a(n,P=[[0, 0]]):
        if n==0: return(1)
        mv1 = [plus(P[-1],x) for x in mo]
        mv2=[x for x in mv1 if x not in P]
        if n==1: return(len(mv2))
        else: return(sum(a(n-1,add(P,x)) for x in mv2))
    [a(n) for n in range(11)]
    # Robert FERREOL, Dec 11 2018

A037245 Number of unrooted self-avoiding walks of n steps on square lattice.

Original entry on oeis.org

1, 2, 4, 9, 22, 56, 147, 388, 1047, 2806, 7600, 20437, 55313, 148752, 401629, 1078746, 2905751, 7793632, 20949045, 56112530, 150561752, 402802376, 1079193821, 2884195424, 7717665979, 20607171273, 55082560423, 146961482787, 392462843329, 1046373230168, 2792115083878
Offset: 1

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Keywords

Comments

Or, number of 2-sided polyedges with n cells. - Ed Pegg Jr, May 13 2009
A walk and its reflection (i.e., exchange start and end of walk, what Hayes calls a "retroreflection") are considered one and the same here. - Joerg Arndt, Jan 26 2018
With A001411 as main input and counting the symmetrical shapes separately, higher terms can be computed efficiently (see formula). - Bert Dobbelaere, Jan 07 2019

Crossrefs

Asymptotically approaches (1/16) * A001411.
Cf. A266549 (closed self-avoiding walks).
Cf. A323188, A323189 (program).

Formula

a(n) = (A001411(n) + A323188(n) + A323189(n) + 4) / 16. - Bert Dobbelaere, Jan 07 2019

Extensions

a(25)-a(27) from Luca Petrone, Dec 20 2015
More terms using formula by Bert Dobbelaere, Jan 07 2019

A116903 Seaweeds(n): number of n-step self-avoiding walks on upper two quadrants grid starting at origin.

Original entry on oeis.org

1, 3, 7, 19, 49, 131, 339, 899, 2345, 6199, 16225, 42811, 112285, 296051, 777411, 2049025, 5384855, 14190509, 37313977, 98324565, 258654441, 681552747, 1793492411, 4725856129, 12439233695, 32778031159, 86295460555, 227399388019, 598784536563, 1577923781445, 4155176578581
Offset: 0

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Author

Giovanni Resta, Feb 15 2006

Keywords

Comments

These walks remind me of fluctuant seaweeds anchored to the sea bottom.

Examples

			The 19 seaweeds of length 3. X marks the origin = anchor point.
........................................................
O-O-O...O-O.. .O-O...O-O....O..O-O-O...O......O..O-O....
....|.....|.. .|.....|......|..|.......|......|....|....
....X...X-O....O.....O-X....O..X..O-O..O-O....O....O-X..
...............|............|.......|....|....|.........
O-O.....O-O....X....O.......O..O....O....X..X-O.......O.
|.|.....|...........|.......|..|....|.................|.
X.O...X-O.....O-O...O-O-X...X..O....X.....O.........O-O.
..............|.|..............|..........|.........|...
..X-O-O-O.....O.X...O-O-O-X....O-X....X-O-O.........X...
........................................................
		

Crossrefs

Extensions

a(23)-a(30) from Scott R. Shannon, Jul 26 2020

A010575 Number of n-step self-avoiding walks on 4-d cubic lattice.

Original entry on oeis.org

1, 8, 56, 392, 2696, 18584, 127160, 871256, 5946200, 40613816, 276750536, 1886784200, 12843449288, 87456597656, 594876193016, 4047352264616, 27514497698984, 187083712725224, 1271271096363128, 8639846411760440, 58689235680164600, 398715967140863864
Offset: 0

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Keywords

Comments

The computation for n=16 took 11.5 days CPU time on a 500MHz Digital Alphastation. The asymptotic behavior lim n->infinity a(n)/mu^n=const is discussed in the MathWorld link. The Pfoertner link provides an illustration of the asymptotic behavior indicating that the connective constant mu is in the range [6.79,6.80]. - Hugo Pfoertner, Dec 14 2002
Computation of the new term a(17) took 16.5 days CPU time on a 1.5GHz Intel Itanium 2 processor. - Hugo Pfoertner, Oct 19 2004

Crossrefs

Programs

  • Fortran
    c A "brute force" Fortran program to count the 4D walks is available at the Pfoertner link.

Formula

a(n) = 8*A366925(n) for n >= 1. - Hugo Pfoertner, Nov 03 2023

Extensions

a(12)-a(16) from Hugo Pfoertner, Dec 14 2002
a(17) from Hugo Pfoertner, Oct 19 2004
a(18) onwards from R. J. Mathar using data from Clisby et al, Aug 31 2007

A038373 Number of n-step self-avoiding paths on quadrant grid starting at quadrant origin.

Original entry on oeis.org

1, 2, 4, 10, 24, 60, 146, 366, 912, 2302, 5800, 14722, 37368, 95304, 243168, 622518, 1594622, 4094768, 10521384, 27085436, 69768478, 179982688, 464564220, 1200563864, 3104192722, 8034256412, 20803994184, 53915334890, 139785953076, 362681515714, 941361260956, 2444866458524, 6351963691964
Offset: 0

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Keywords

Crossrefs

Formula

a(n) = 2 * A046170(n) for n >= 1. - Siqi Wang, Jul 15 2022

Extensions

a(25)-a(32) from Bert Dobbelaere, Jan 05 2019

A077482 Number of self-avoiding walks on square lattice trapped after n steps.

Original entry on oeis.org

1, 2, 11, 25, 95, 228, 752, 1860, 5741, 14477, 42939, 109758, 317147, 818229, 2322512, 6030293, 16900541, 44079555, 122379267, 320227677, 882687730, 2315257359, 6346076015, 16675422679, 45502168379, 119728011251, 325510252108, 857400725204
Offset: 7

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Author

Hugo Pfoertner, Nov 07 2002

Keywords

Comments

Only 1/8 of all possible walks is counted by selecting the first step in +x direction and requiring the first step changing y to be positive.

Examples

			a(7) = 1 because there is only 1 self-trapping walk with 7 steps: (0,0)(1,0)(1,1)(1,2)(0,2)(-1,2)(-1,1)(0,1); a(8) = 2 because there are 2 self-trapping walks with 8 steps: (0,0)(1,0)(2,0)(2,1)(2,2)(1,2)(0,2)(0,1)(1,1) and (0,0)(1,0)(1,1)(2,1)(3,1)(3,0)(3,-1)(2,-1)(2,0).
		

References

  • See references given for A001411.

Crossrefs

Programs

  • Fortran
    c See Hugo Pfoertner link.

Extensions

a(26)-a(28) from Alois P. Heinz, Jun 16 2011
a(29)-a(34) from Bert Dobbelaere, Jan 03 2019

A001336 Number of n-step self-avoiding walks on f.c.c. lattice.

Original entry on oeis.org

1, 12, 132, 1404, 14700, 152532, 1573716, 16172148, 165697044, 1693773924, 17281929564, 176064704412, 1791455071068, 18208650297396, 184907370618612, 1876240018679868, 19024942249966812, 192794447005403916, 1952681556794601732, 19767824914170222996
Offset: 0

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Author

Keywords

References

  • B. D. Hughes, Random Walks and Random Environments, Oxford 1995, vol. 1, p. 460.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Extensions

a(15) from Bert Dobbelaere, Jan 13 2019
Terms a(16) and beyond from Schram et al. added by Andrey Zabolotskiy, Feb 02 2022

A078528 Number of unconstrained walks on square lattice trapped after n steps.

Original entry on oeis.org

1, 1, 2, 5, 15, 30, 76, 170, 422, 961, 2339, 5390, 12977, 30059, 71918, 167019, 397691, 924931, 2194478, 5107991, 12085695, 28143758, 66442935, 154759821, 364706675, 849562628
Offset: 7

Views

Author

Hugo Pfoertner, Nov 27 2002

Keywords

Comments

See under A078527. In the probability sum in A077483 and A078526 the unconstrained walks are responsible for the occurrence of 3^(n-1) in the denominator of P(n).

Examples

			a(7)=1 because the unique shortest walk contains no constrained steps. a(10)=5: See illustration in "5 Unconstrained and 7 maximally 2-constrained walks of length 10" given at link.
		

Crossrefs

Programs

  • Fortran
    c Program provided at given link

Extensions

a(24)-a(32) from Sean A. Irvine, Jul 03 2025
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