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 1-7 of 7 results.

A076832 Triangle T(n,k), read by rows, giving the total number of inequivalent binary linear [n,i] codes with no column of zeros, summed for i <= k (n >= 1, 1 <= k <= n).

Original entry on oeis.org

1, 1, 2, 1, 3, 4, 1, 4, 7, 8, 1, 5, 11, 15, 16, 1, 7, 19, 30, 35, 36, 1, 8, 29, 56, 73, 79, 80, 1, 10, 44, 107, 161, 186, 193, 194, 1, 12, 66, 200, 363, 462, 497, 505, 506, 1, 14, 96, 372, 837, 1222, 1392, 1439, 1448, 1449, 1, 16, 136, 680, 1963, 3435, 4282
Offset: 1

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Author

N. J. A. Sloane, Nov 21 2002

Keywords

Comments

From Petros Hadjicostas, Sep 30 2019: (Start)
It seems that Harald Fripertinger at his website defines T(n,k) = T(n,n) for k > n (and thus he gets an orthogonal array). It seems that T(n,n) = A034343(n).
It seems that T(n,k=2) = A001399(n) for n >= 2 (with A001399(n=1) = T(1,1)); T(n,k=3) = A034337(n) for n >= 3 (with A034337(n) = T(n,n) for 1 <= n <= 2); T(n,k=4) = A034338(n) for n >= 4 (with A034338(n) = T(n,n) for 1 <= n <= 3); and so on. See the Crossrefs below for more information.
To get the g.f. of column k (starting at n = 0 with T(n=0,k) := 1 rather than at n = k), modify the Sage program below (cf. function f).
(End)

Examples

			Triangle T(n,k) (with rows n >= 1 and columns k >= 1) begins as follows:
  1;
  1,  2;
  1,  3,  4;
  1,  4,  7,   8;
  1,  5, 11,  15,  16;
  1,  7, 19,  30,  35,  36;
  1,  8, 29,  56,  73,  79,  80;
  1, 10, 44, 107, 161, 186, 193, 194; ...
		

Crossrefs

Columns give truncated versions of A001399 (k = 2), A034337 (k = 3), A034338 (k = 4), A034339 (k = 5), A034340 (k = 6), A034341 (k = 7), A034342 (k = 8), and A034343 (? main diagonal).

Programs

  • Maple
    # We illustrate how to get a g.f. for column k in Maple when k is small.
    with(GroupTheory);
    G := ProjectiveGeneralLinearGroup(4, 2);
    GroupOrder(G);
    # We get that the order is 20160.
    f:=CycleIndexPolynomial(G, [x||(1..20160)]);
    # We get
    # 1/20160*x1^15 + 1/192*x1^7*x2^4 + 1/96*x1^3*x2^6 + 1/16*x1^3*x2^2*x4^2 +
    # 1/18*x1^3*x3^4 + 1/6*x1*x2*x3^2*x6 + 1/8*x1*x2*x4^3 + 1/180*x3^5 + 2/7*x1*x7^2 +
    # 1/12*x3*x6^2 + 1/15*x5^3 + 2/15*x15
    # The only dummy variables that appear are x1, x2, x3, x4, x5, x6, x7, and x15.
    g:=subs(x1 = 1/(1 - y), subs(x2 = 1/(-y^2 + 1), subs(x3 = 1/(-y^3 + 1), subs(x4 = 1/(-y^4 + 1), subs(x5 = 1/(-y^5 + 1), subs(x6 = 1/(-y^6 + 1), subs(x7 = 1/(-y^7 + 1), subs(x15 = 1/(-y^15 + 1), f))))))));
    # Then we take a Taylor expansion of the above g.f.
    taylor(g,y=0,50);
    # We get a Taylor expansion for column k = 4 (i.e., A034338).
    # Petros Hadjicostas, Sep 30 2019
  • Sage
    # Fripertinger's method to find the g.f. of column k for small k:
    def A076832col(k, length):
        G = PSL(k, GF(2))
        D = G.cycle_index()
        f = sum(i[1]*prod(1/(1-x^j) for j in i[0]) for i in D)
        return f.taylor(x, 0, length).list()
    # For instance the Taylor expansion for column k = 4 gives A034338:
    print(A076832col(4, 30)) # Petros Hadjicostas, Sep 30 2019

Extensions

Revised by N. J. A. Sloane, Mar 01 2004

A034343 Number of inequivalent binary linear codes of length n and any dimension k <= n containing no column of zeros.

Original entry on oeis.org

1, 2, 4, 8, 16, 36, 80, 194, 506, 1449, 4631, 17106, 74820, 404283, 2815595, 26390082, 344330452, 6365590987, 167062019455, 6182453531508, 319847262335488, 22968149462624180, 2277881694784784852
Offset: 1

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Author

Keywords

Comments

Comment from N. J. A. Sloane, Nov 27 2017 (Start)
Also, (by taking duals) number of inequivalent binary linear codes of length n and any dimension k <= n containing no codewords of weight 1.
It follows from the theorem on page 64 of Schwarzenberger (1980), this is also the number of Bravais types of orthogonal lattices in dimension n. (End)
Also the number of loopless binary matroids on n points.

References

  • R. L. E. Schwarzenberger, N-Dimensional Crystallography. Pitman, London, 1980, pages 64 and 65.
  • M. Wild, Enumeration of binary and ternary matroids and other applications of the Brylawski-Lucas Theorem, Preprint No. 1693, Tech. Hochschule Darmstadt, 1994

Crossrefs

Formula

a(n) = A076832(n,n). - Petros Hadjicostas, Sep 30 2019

A034338 Number of binary [ n,4 ] codes of dimension <= 4 without zero columns.

Original entry on oeis.org

1, 2, 4, 8, 15, 30, 56, 107, 200, 372, 680, 1241, 2221, 3938, 6880, 11860, 20148, 33778, 55814, 91007, 146392, 232458, 364462, 564560, 864230, 1308160, 1958700, 2902417, 4258009, 6187350, 8908680, 12714829, 17994860, 25262928, 35193094, 48664341, 66814595, 91109910, 123426848, 166156091
Offset: 1

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Author

Keywords

Comments

To get the g.f. of this sequence (with a constant 1), modify the Sage program below (cf. function f). It is too complicated to write it here. See the link below. - Petros Hadjicostas, Sep 30 2019

Crossrefs

Column k=4 of A076832 (starting at n=4).
Cf. A034337.

Programs

  • Sage
    # Fripertinger's method to find the g.f. of column k for small k:
    def Tcol(k, length):
        G = PSL(k, GF(2))
        D = G.cycle_index()
        f = sum(i[1]*prod(1/(1-x^j) for j in i[0]) for i in D)
        return f.taylor(x, 0, length).list()
    # For instance the Taylor expansion for column k = 4 gives a(n):
    print(Tcol(4, 30)) # Petros Hadjicostas, Sep 30 2019

Extensions

More terms from Petros Hadjicostas, Sep 30 2019

A034339 Number of binary [ n,5 ] codes of dimension <= 5 without zero columns.

Original entry on oeis.org

1, 2, 4, 8, 16, 35, 73, 161, 363, 837, 1963, 4721, 11477, 28220, 69692, 171966, 421972, 1025811, 2462143, 5821962, 13540152, 30942230, 69443492, 153038397, 331208859, 704147310, 1471172776, 3022148872, 6107363788, 12148478891, 23799499067, 45944968466, 87452845802, 164214143935
Offset: 1

Views

Author

Keywords

Comments

To get the g.f. of this sequence (with a constant 1), modify the Sage program below (cf. function f). It is too complicated to write it here. See the link below. - Petros Hadjicostas, Sep 30 2019

Crossrefs

Column k=5 of A076832 (starting at n=5).
Cf. A034337.

Programs

  • Sage
    # Fripertinger's method to find the g.f. of column k for small k:
    def Tcol(k, length):
        G = PSL(k, GF(2))
        D = G.cycle_index()
        f = sum(i[1]*prod(1/(1-x^j) for j in i[0]) for i in D)
        return f.taylor(x, 0, length).list()
    # For instance the Taylor expansion for column k = 5 gives a(n):
    print(Tcol(5, 30)) # Petros Hadjicostas, Sep 30 2019

Extensions

More terms from Petros Hadjicostas, Sep 30 2019

A034340 Number of binary [ n,6 ] codes of dimension <= 6 without zero columns.

Original entry on oeis.org

1, 2, 4, 8, 16, 36, 79, 186, 462, 1222, 3435, 10397, 33578, 115624, 419789, 1585217, 6130130, 23928972, 93161541, 358570997, 1356178991, 5021267644, 18160079508, 64086748267, 220608700157, 740874170362, 2428425908049, 7773761586051, 24320543815203, 74418574119634, 222890851257632
Offset: 1

Views

Author

Keywords

Comments

To get the g.f. of this sequence (with a constant 1), modify the Sage program below (cf. function f). It is too complicated to write it here. See the link below. - Petros Hadjicostas, Sep 30 2019

Crossrefs

Column k=6 of A076832 (starting at n=6).
Cf. A034337.

Programs

  • Sage
    # Fripertinger's method to find the g.f. of column k for small k:
    def Tcol(k, length):
        G = PSL(k, GF(2))
        D = G.cycle_index()
        f = sum(i[1]*prod(1/(1-x^j) for j in i[0]) for i in D)
        return f.taylor(x, 0, length).list()
    # For instance the Taylor expansion for column k = 6 gives a(n):
    print(Tcol(6, 30)) #  Petros Hadjicostas, Sep 30 2019

Extensions

More terms from Petros Hadjicostas, Sep 30 2019

A034341 Number of binary [ n,7 ] codes of dimension <= 7 without zero columns.

Original entry on oeis.org

1, 2, 4, 8, 16, 36, 80, 193, 497, 1392, 4282, 14805, 57875, 258894, 1321280, 7570495, 47305333, 311742256, 2103025726, 14206632939, 94726167427, 618051904983, 3927156178649, 24243834619157, 145277300343585, 844969890205372, 4772180415241078, 26189419064610811, 139774809119967723
Offset: 1

Views

Author

Keywords

Comments

To get the g.f. of this sequence (with a constant 1), modify the Sage program below (cf. function f). It is too complicated to write it here. - Petros Hadjicostas, Sep 30 2019

Crossrefs

Column k=7 of A076832 (starting at n=7).
Cf. A034337.

Programs

  • Sage
    # Fripertinger's method to find the g.f. of column k for small k:
    def Tcol(k, length):
        G = PSL(k, GF(2))
        D = G.cycle_index()
        f = sum(i[1]*prod(1/(1-x^j) for j in i[0]) for i in D)
        return f.taylor(x, 0, length).list()
    # For instance the Taylor expansion for column k = 7 gives a(n):
    print(Tcol(7, 30)) # Petros Hadjicostas, Sep 30 2019

Extensions

More terms by Petros Hadjicostas, Sep 30 2019

A034342 Number of binary [ n,8 ] codes of dimension <= 8 without zero columns.

Original entry on oeis.org

1, 2, 4, 8, 16, 36, 80, 194, 505, 1439, 4559, 16580, 70491, 361339, 2278637, 17745061, 166540680, 1794040168, 20987476447, 254684454328, 3107605995993, 37418101305011, 439995775004885, 5025781692126252, 55627454599068011, 596148004493419480, 6186335017615750870, 62196701669630203157
Offset: 1

Views

Author

Keywords

Comments

To get the g.f. of this sequence (with a constant 1), modify the Sage program below (cf. function f). It is too complicated to write it here. - Petros Hadjicostas, Sep 30 2019

Crossrefs

Column k=8 of A076832 (starting at n=8).
Cf. A034337.

Programs

  • Sage
    # Fripertinger's method to find the g.f. of column k for small k:
    def Tcol(k, length):
        G = PSL(k, GF(2))
        D = G.cycle_index()
        f = sum(i[1]*prod(1/(1-x^j) for j in i[0]) for i in D)
        return f.taylor(x, 0, length).list()
    # For instance the Taylor expansion for column k = 8 gives a(n):
    print(Tcol(8, 30)) # Petros Hadjicostas, Sep 30 2019

Extensions

More terms from Petros Hadjicostas, Sep 30 2019
Showing 1-7 of 7 results.