A034337 Number of inequivalent binary [ n,3 ] codes of dimension <= 3 without zero columns.

1, 2, 4, 7, 11, 19, 29, 44, 66, 96, 136, 193, 265, 361, 485, 643, 841, 1093, 1401, 1782, 2248, 2811, 3487, 4301, 5263, 6403, 7745, 9315, 11141, 13266, 15714, 18534, 21768, 25461, 29663, 34439, 39835, 45926, 52780, 60469, 69071, 78684, 89382, 101276, 114468, 129066, 145186, 162967, 182523

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Discrete algorithms at the University of Bayreuth, Symmetrica. [This package was used by Harald Fripertinger to compute T_{nk2} = A076832(n,k) using the cycle index of PGL_k(2). Here k = 3. That is, a(n) = T_{n,3,2} = A076832(n,3), but we start at n = 1 rather than at n = 3.]
• Harald Fripertinger, Isometry Classes of Codes.
• Harald Fripertinger, Tnk2: Number of the isometry classes of all binary (n,r)-codes for 1 <= r <= k without zero-columns. [This is a rectangular array whose lower triangle is A076832(n,k). Here we have column k = 3.]
• Harald Fripertinger, Enumeration of isometry classes of linear (n,k)-codes over GF(q) in SYMMETRICA, Bayreuther Mathematische Schriften 49 (1995), 215-223. [See pp. 216-218. A C-program is given for calculating T_{nk2} in Symmetrica. Here k = 3.]
• Harald Fripertinger, Cycle of indices of linear, affine, and projective groups, Linear Algebra and its Applications 263 (1997), 133-156. [See p. 152 for the computation of T_{nk2} = A076832(n,k). Here k = 3.]
• H. Fripertinger and A. Kerber, Isometry classes of indecomposable linear codes. In: G. Cohen, M. Giusti, T. Mora (eds), Applied Algebra, Algebraic Algorithms and Error-Correcting Codes, 11th International Symposium, AAECC 1995, Lect. Notes Comp. Sci. 948 (1995), pp. 194-204. [The notation for A076832(n,k) is T_{nk2}. Here k = 3.]
• David Slepian, Some further theory of group codes, Bell System Tech. J. 39(5) (1960), 1219-1252.
• David Slepian, Some further theory of group codes, Bell System Tech. J. 39(5) (1960), 1219-1252.
• Wikipedia, Cycle index.
• Wikipedia, Projective linear group.

Crossrefs

Column k=3 of A076832 (starting at n=3).

Cf. A034253.

Programs

SageMath

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 = 3 gives a(n):
print(Tcol(3, 30)) # Petros Hadjicostas, Sep 30 2019

Formula

G.f.: -(x^10 - x^8 + x^6 + x^5 + x^4 - x^2 + 1)*(x^4 - x^3 + x^2 - x + 1)/((x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)*(x^2 + x + 1)^2*(x^2 + 1)*(x + 1)^2*(x - 1)^7). - Petros Hadjicostas, Sep 30 2019

Extensions

More terms by Petros Hadjicostas, Sep 30 2019