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 1-6 of 6 results.

A079157 Sum of square displacements over all self-avoiding walks on cubic lattice trapped after n steps. Numerator of mean square displacement a(n)/A077817(n).

Original entry on oeis.org

5, 50, 529, 3870, 28900, 185014, 1191698, 7080332, 42072344, 238337862
Offset: 11

Views

Author

Hugo Pfoertner, Dec 30 2002

Keywords

Examples

			a(12)=50 because the A077817(12)=20 trapped walks stop at 5*(1,1,0)->d^2=2, 5*(2,0,0)->d^2=4, 10*(1,0,1)->d^2=2. So, a(12)=5*2+5*4+10*2=50. See "Enumeration of all self-trapping walks of length 12" at link.
		

Crossrefs

Cf. A077817, A078605, A079158 (corresponding Manhattan distance sum).

Programs

  • Fortran
    c Program for distance counting available at link.

Formula

a(n) = Sum_{l=1..A077817(n)} (i_l^2 + j_l^2 + k_l^2) where (i_l, j_l, k_l) are the end points of all different self-avoiding walks trapped after n steps.

Extensions

a(15) corrected and a(19)-a(20) from Sean A. Irvine, Jul 31 2025

A377161 a(n) is the numerator of the probability that a self-avoiding random walk on the cubic lattice is trapped after n steps.

Original entry on oeis.org

8, 38, 637, 9759, 86221819, 28522360751, 583791967829, 1801511107253, 6467456149881773
Offset: 11

Views

Author

Hugo Pfoertner, Oct 20 2024

Keywords

Examples

			8/1953125, 38/9765625, 637/58593750, 9759/976562500, 86221819/4687500000000, 28522360751/1687500000000000, 583791967829/22500000000000000, ...
		

Crossrefs

A377162 are the corresponding denominators.
Cf. A001412, A077817, A077818 (see there for more information), A077819, A077820.

Formula

a(n)/A377162(n) = A077818(n) / (5^(n-1) * 3^A077819(n) * 2^A077820(n)).

A077818 a(n) is the numerator of the probability P(n) of the occurrence of a 3-dimensional self-trapping walk of length n.

Original entry on oeis.org

40, 190, 15925, 48795, 86221819, 28522360751, 583791967829, 1801511107253, 32337280749408865
Offset: 11

Views

Author

Hugo Pfoertner, Nov 17 2002

Keywords

Comments

A comparison of the exact probabilities with simulation results obtained for 1.1*10^9 random walks is given under "Results of simulation, comparison with exact probabilities" in the first link. The behavior of P(n) for larger values of n is illustrated in "Probability density for the number of steps before trapping occurs" at the same location. P(n) has a maximum around n~=600 (P(600)~=1/4760) and drops exponentially for large n (P(45000)~=1/10^9). The average walk length determined by the numerical simulation is sum n=11..infinity (n*P(n))=3953.65 +-0.20.
A more accurate value for this length, determined from a simulation with 27*10^9 walks, is 3953.8+-0.1 (A378903). - Hugo Pfoertner, Dec 15 2024

Examples

			a(13)=15925, A077819(13)=A077820(13)=1 because there are 5 different probabilities for the 1832 (=8*A077817(13)) walks: 256 walks with probability p1=1/125000000, 88 with p2=1/146484375, 600 with p3=1/156250000, 728 with p4=1/146484375 and 160 with p5=1/244140625. P(13)=256*p1+88*p2+600*p3+728*p4+160*p5=637/(6*5^10)=25*637/(5^12*6)= 15295/(5^(13-1)*3^1*2^1)
		

References

  • See under A001412.
  • More references are given in the sci.math NG posting in the second link.

Crossrefs

Programs

  • Fortran
    c Program provided at first link

Formula

P(n) = a(n) / (5^(n-1) * 3^A077819(n) * 2^A077820(n)) = A377161(n)/A377162(n).

A378903 Decimal expansion of the expected number of steps to termination by self-trapping of a self-avoiding random walk on the cubic lattice.

Original entry on oeis.org

3, 9, 5, 3, 7
Offset: 4

Views

Author

Hugo Pfoertner, Dec 14 2024

Keywords

Comments

See A077818 for more information and links. Since a more accurate value is probably 3953.78..., one should currently use 3953.8 +- 0.1 as a safe estimate.

Examples

			3953.7...
		

Crossrefs

A079158 Sum of end-to-end Manhattan distances over all self-avoiding walks on cubic lattice trapped after n steps.

Original entry on oeis.org

5, 40, 399, 2472, 17436, 98400, 601626, 3238694, 18355742, 96020478
Offset: 11

Views

Author

Hugo Pfoertner, Dec 30 2002

Keywords

Comments

Mean Manhattan displacement is a(n)/A077817(n).
See also "Comparison of average Euclidean and Manhattan displacements" at link

Examples

			a(12)=40 because the A077817(12)=20 trapped walks stop at 5*(1,1,0)->d=2, 5*(2,0,0)->d=2, 10*(1,0,1)->d=2, so a(12)=5*2+5*2+10*2=40. See "Enumeration of all self-trapping walks of length 12" at link.
		

Crossrefs

Cf. A077817, A079156, A079157 (corresponding squared distance sum).

Programs

  • Fortran
    c Program for distance counting available at link.

Formula

a(n)= Sum_{l=1..A077817(n)} (|i_l| + |j_l| + |k_l|) where (i_l, j_l, k_l) are the end points of all different self-avoiding walks trapped after n steps.

Extensions

a(19)-a(20) from Sean A. Irvine, Jul 31 2025

A107069 Number of self-avoiding walks of length n on an infinite triangular prism starting at the origin.

Original entry on oeis.org

1, 4, 12, 34, 90, 222, 542, 1302, 3058, 7186, 16714, 38670, 89358, 205710, 472906, 1086138, 2491666, 5713318, 13094950, 30003190, 68731010, 157423986, 360530346, 825626942, 1890615518, 4329196974, 9912914314, 22698017834, 51972012258, 119000208806
Offset: 0

Views

Author

Jonathan Vos Post, May 10 2005

Keywords

Comments

The discrete space in which the walking happens is a triangular prism infinite in both directions along the x-axis. One vertex is the root, the origin. The basis is the set of single-step vectors, which we abbreviate as l (left), r (right), c (one step "clockwise" around the triangle) and c- (one step counterclockwise, more properly denoted c^-1).

Examples

			a(0) = 1, as there is one self-avoiding walk of length 0, namely the null-walk (the walk whose steps are the null set).
a(1) = 4 because (using the terminology in the Comment), the 4 possible 1-step walks are W_1 = {l,r,c,c-}.
a(2) = 12 because the set of legal 2-step walks are {l^2, lc, lc-, r^2, rc, rc-, c^2, cl, cr, c^-2, c-l, c-r}.
a(3) = 34 because we have every W_2 concatenated with {l,r,c,c-} except for those with immediate violations (lr etc.) and those two which go in a triangle {c^3, c^-3}; hence a(3) = 3*a(2) - 2 = 3*12 - 2 = 36 - 2 = 34.
		

Crossrefs

Programs

  • Python
    w = [[[(0, 0)]]]
    for n in range(1, 15):
        nw = []
        for walk in w[-1]:
            (x, t) = walk[-1]
            nss = [(x-1, t), (x+1, t), (x, (t+1)%3), (x, (t-1)%3)]
            for ns in nss:
                if ns not in walk:
                    nw.append(walk[:] + [ns])
        w.append(nw)
    print([len(x) for x in w])
    # Andrey Zabolotskiy, Sep 19 2019

Extensions

a(4) and a(5) corrected, a(6)-a(14) added by Andrey Zabolotskiy, Sep 19 2019
More terms from Andrey Zabolotskiy, Dec 04 2023
Showing 1-6 of 6 results.